Vulnerability Mapping:
DISCOURAGEDThis CWE ID should not be used to map to real-world vulnerabilities Abstraction: ClassClass - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
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Description
The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
Extended Description
Limited resources include memory, file system storage, database connection pool entries, and CPU. If an attacker can trigger the allocation of these limited resources, but the number or size of the resources is not controlled, then the attacker could cause a denial of service that consumes all available resources. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
There are at least three distinct scenarios which can commonly lead to resource exhaustion:
Lack of throttling for the number of allocated resources
Losing all references to a resource before reaching the shutdown stage
Not closing/returning a resource after processing
Resource exhaustion problems are often result due to an incorrect implementation of the following situations:
Error conditions and other exceptional circumstances.
Confusion over which part of the program is responsible for releasing the resource.
Alternate Terms
Resource Exhaustion
Common Consequences
This table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
The most common result of resource exhaustion is denial of service. The product may slow down, crash due to unhandled errors, or lock out legitimate users.
Access Control Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
Potential Mitigations
Phase: Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
Phase: Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either:
recognizes the attack and denies that user further access for a given amount of time, or
uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Phase: Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
Phase: Implementation
Ensure that all failures in resource allocation place the system into a safe posture.
Relationships
This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Research Concepts" (CWE-1000)
Nature
Type
ID
Name
ChildOf
Pillar - a weakness that is the most abstract type of weakness and represents a theme for all class/base/variant weaknesses related to it. A Pillar is different from a Category as a Pillar is still technically a type of weakness that describes a mistake, while a Category represents a common characteristic used to group related things.
Class - a weakness that is described in a very abstract fashion, typically independent of any specific language or technology. More specific than a Pillar Weakness, but more general than a Base Weakness. Class level weaknesses typically describe issues in terms of 1 or 2 of the following dimensions: behavior, property, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
Nature
Type
ID
Name
MemberOf
View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
Base - a weakness
that is still mostly independent of a resource or technology, but with sufficient details to provide specific methods for detection and prevention. Base level weaknesses typically describe issues in terms of 2 or 3 of the following dimensions: behavior, property, technology, language, and resource.
The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.
Phase
Note
Operation
Architecture and Design
Implementation
Applicable Platforms
This listing shows possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.
Languages
Class: Not Language-Specific (Undetermined Prevalence)
There are no limits to runnables. Potentially an attacker could cause resource problems very quickly.
Example 2
This code allocates a socket and forks each time it receives a new connection.
(bad code)
Example Language: C
sock=socket(AF_INET, SOCK_STREAM, 0); while (1) {
newsock=accept(sock, ...); printf("A connection has been accepted\n"); pid = fork();
}
The program does not track how many connections have been made, and it does not limit the number of connections. Because forking is a relatively expensive operation, an attacker would be able to cause the system to run out of CPU, processes, or memory by making a large number of connections. Alternatively, an attacker could consume all available connections, preventing others from accessing the system remotely.
Example 3
In the following example a server socket connection is used to accept a request to store data on the local file system using a specified filename. The method openSocketConnection establishes a server socket to accept requests from a client. When a client establishes a connection to this service the getNextMessage method is first used to retrieve from the socket the name of the file to store the data, the openFileToWrite method will validate the filename and open a file to write to on the local file system. The getNextMessage is then used within a while loop to continuously read data from the socket and output the data to the file until there is no longer any data from the socket.
(bad code)
Example Language: C
int writeDataFromSocketToFile(char *host, int port) {
char filename[FILENAME_SIZE]; char buffer[BUFFER_SIZE]; int socket = openSocketConnection(host, port);
if (socket < 0) {
printf("Unable to open socket connection"); return(FAIL);
} if (getNextMessage(socket, filename, FILENAME_SIZE) > 0) {
if (openFileToWrite(filename) > 0) {
while (getNextMessage(socket, buffer, BUFFER_SIZE) > 0){
if (!(writeToFile(buffer) > 0))
break;
}
} closeFile();
} closeSocket(socket);
}
This example creates a situation where data can be dumped to a file on the local file system without any limits on the size of the file. This could potentially exhaust file or disk resources and/or limit other clients' ability to access the service.
Example 4
In the following example, the processMessage method receives a two dimensional character array containing the message to be processed. The two-dimensional character array contains the length of the message in the first character array and the message body in the second character array. The getMessageLength method retrieves the integer value of the length from the first character array. After validating that the message length is greater than zero, the body character array pointer points to the start of the second character array of the two-dimensional character array and memory is allocated for the new body character array.
(bad code)
Example Language: C
/* process message accepts a two-dimensional character array of the form [length][body] containing the message to be processed */ int processMessage(char **message) {
char *body;
int length = getMessageLength(message[0]);
if (length > 0) {
body = &message[1][0]; processMessageBody(body); return(SUCCESS);
} else {
printf("Unable to process message; invalid message length"); return(FAIL);
}
}
This example creates a situation where the length of the body character array can be very large and will consume excessive memory, exhausting system resources. This can be avoided by restricting the length of the second character array with a maximum length check
Also, consider changing the type from 'int' to 'unsigned int', so that you are always guaranteed that the number is positive. This might not be possible if the protocol specifically requires allowing negative values, or if you cannot control the return value from getMessageLength(), but it could simplify the check to ensure the input is positive, and eliminate other errors such as signed-to-unsigned conversion errors (CWE-195) that may occur elsewhere in the code.
(good code)
Example Language: C
unsigned int length = getMessageLength(message[0]); if ((length > 0) && (length < MAX_LENGTH)) {...}
Example 5
In the following example, a server object creates a server socket and accepts client connections to the socket. For every client connection to the socket a separate thread object is generated using the ClientSocketThread class that handles request made by the client through the socket.
(bad code)
Example Language: Java
public void acceptConnections() {
try {
ServerSocket serverSocket = new ServerSocket(SERVER_PORT); int counter = 0; boolean hasConnections = true; while (hasConnections) {
Socket client = serverSocket.accept(); Thread t = new Thread(new ClientSocketThread(client)); t.setName(client.getInetAddress().getHostName() + ":" + counter++); t.start();
} serverSocket.close();
} catch (IOException ex) {...}
}
In this example there is no limit to the number of client connections and client threads that are created. Allowing an unlimited number of client connections and threads could potentially overwhelm the system and system resources.
The server should limit the number of client connections and the client threads that are created. This can be easily done by creating a thread pool object that limits the number of threads that are generated.
(good code)
Example Language: Java
public static final int SERVER_PORT = 4444; public static final int MAX_CONNECTIONS = 10; ...
public void acceptConnections() {
try {
ServerSocket serverSocket = new ServerSocket(SERVER_PORT); int counter = 0; boolean hasConnections = true; while (hasConnections) {
hasConnections = checkForMoreConnections(); Socket client = serverSocket.accept(); Thread t = new Thread(new ClientSocketThread(client)); t.setName(client.getInetAddress().getHostName() + ":" + counter++); ExecutorService pool = Executors.newFixedThreadPool(MAX_CONNECTIONS); pool.execute(t);
} serverSocket.close();
} catch (IOException ex) {...}
}
Example 6
In the following example, the serve function receives an http request and an http response writer. It reads the entire request body.
(bad code)
Example Language: Go
func serve(w http.ResponseWriter, r *http.Request) {
var body []byte
if r.Body != nil {
if data, err := io.ReadAll(r.Body); err == nil {
body = data
}
}
}
Because ReadAll is defined to read from src until EOF, it does not treat an EOF from Read as an error to be reported. This example creates a situation where the length of the body supplied can be very large and will consume excessive memory, exhausting system resources. This can be avoided by ensuring the body does not exceed a predetermined length of bytes.
MaxBytesReader prevents clients from accidentally or maliciously sending a large request and wasting server resources. If possible, the code could be changed to tell ResponseWriter to close the connection after the limit has been reached.
(good code)
Example Language: Go
func serve(w http.ResponseWriter, r *http.Request) {
var body []byte
const MaxRespBodyLength = 1e6
if r.Body != nil {
Chain: Python library does not limit the resources used to process images that specify a very large number of bands (CWE-1284), leading to excessive memory consumption (CWE-789) or an integer overflow (CWE-190).
Chain: anti-virus product encounters a malformed file but returns from a function without closing a file descriptor (CWE-775) leading to file descriptor consumption (CWE-400) and failed scans.
Detection Methods
Automated Static Analysis
Automated static analysis typically has limited utility in recognizing resource exhaustion problems, except for program-independent system resources such as files, sockets, and processes. For system resources, automated static analysis may be able to detect circumstances in which resources are not released after they have expired. Automated analysis of configuration files may be able to detect settings that do not specify a maximum value.
Automated static analysis tools will not be appropriate for detecting exhaustion of custom resources, such as an intended security policy in which a bulletin board user is only allowed to make a limited number of posts per day.
Effectiveness: Limited
Automated Dynamic Analysis
Certain automated dynamic analysis techniques may be effective in spotting resource exhaustion problems, especially with resources such as processes, memory, and connections. The technique may involve generating a large number of requests to the product within a short time frame.
Effectiveness: Moderate
Fuzzing
While fuzzing is typically geared toward finding low-level implementation bugs, it can inadvertently find resource exhaustion problems. This can occur when the fuzzer generates a large number of test cases but does not restart the targeted product in between test cases. If an individual test case produces a crash, but it does not do so reliably, then an inability to handle resource exhaustion may be the cause.
Effectiveness: Opportunistic
Memberships
This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.
Nature
Type
ID
Name
MemberOf
Category - a CWE entry that contains a set of other entries that share a common characteristic.
View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).
View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).
View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).
View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).
(this CWE ID should not be used to map to real-world vulnerabilities)
Reason: Frequent Misuse
Rationale:
CWE-400 is intended for incorrect behaviors in which the product is expected to track and restrict how many resources it consumes, but CWE-400 is often misused because it is conflated with the "technical impact" of vulnerabilities in which resource consumption occurs. It is sometimes used for low-information vulnerability reports. It is a level-1 Class (i.e., a child of a Pillar).
Comments:
Closely analyze the specific mistake that is causing resource consumption, and perform a CWE mapping for that mistake. Consider children/descendants such as CWE-770: Allocation of Resources Without Limits or Throttling, CWE-771: Missing Reference to Active Allocated Resource, CWE-410: Insufficient Resource Pool, CWE-772: Missing Release of Resource after Effective Lifetime, CWE-834: Excessive Iteration, CWE-405: Asymmetric Resource Consumption (Amplification), and others.
Notes
Theoretical
Vulnerability theory is largely about how behaviors and resources interact. "Resource exhaustion" can be regarded as either a consequence or an attack, depending on the perspective. This entry is an attempt to reflect the underlying weaknesses that enable these attacks (or consequences) to take place.
Other
Database queries that take a long time to process are good DoS targets. An attacker would have to write a few lines of Perl code to generate enough traffic to exceed the site's ability to keep up. This would effectively prevent authorized users from using the site at all. Resources can be exploited simply by ensuring that the target machine must do much more work and consume more resources in order to service a request than the attacker must do to initiate a request.
A prime example of this can be found in old switches that were vulnerable to "macof" attacks (so named for a tool developed by Dugsong). These attacks flooded a switch with random IP and MAC address combinations, therefore exhausting the switch's cache, which held the information of which port corresponded to which MAC addresses. Once this cache was exhausted, the switch would fail in an insecure way and would begin to act simply as a hub, broadcasting all traffic on all ports and allowing for basic sniffing attacks.
Maintenance
"Resource consumption" could be interpreted as a consequence instead of an insecure behavior, so this entry is being considered for modification. It appears to be referenced too frequently when more precise mappings are available. Some of its children, such as CWE-771, might be better considered as a chain.
Maintenance
The Taxonomy_Mappings to ISA/IEC 62443 were added in CWE 4.10, but they are still under review and might change in future CWE versions. These draft mappings were performed by members of the "Mapping CWE to 62443" subgroup of the CWE-CAPEC ICS/OT Special Interest Group (SIG), and their work is incomplete as of CWE 4.10. The mappings are included to facilitate discussion and review by the broader ICS/OT community, and they are likely to change in future CWE versions.
Taxonomy Mappings
Mapped Taxonomy Name
Node ID
Fit
Mapped Node Name
CLASP
Resource exhaustion (file descriptor, disk space, sockets, ...)
OWASP Top Ten 2004
A9
CWE More Specific
Denial of Service
WASC
10
Denial of Service
WASC
41
XML Attribute Blowup
The CERT Oracle Secure Coding Standard for Java (2011)
SER12-J
Avoid memory and resource leaks during serialization
The CERT Oracle Secure Coding Standard for Java (2011)
[REF-386] Joao Antunes, Nuno Ferreira Neves
and Paulo Verissimo. "Detection and Prediction of Resource-Exhaustion Vulnerabilities". Proceedings of the IEEE International Symposium on Software Reliability Engineering (ISSRE). 2008-11.
<http://homepages.di.fc.ul.pt/~nuno/PAPERS/ISSRE08.pdf>.
Description
This table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Relevant to the view "Weaknesses for Simplified Mapping of Published Vulnerabilities" (CWE-1003)
