CWE

CWE-772 – Missing Release of Resource after Effective Lifetime

Read Time:1 Minute, 45 Second

Description

The software does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.

When a resource is not released after use, it can allow attackers to cause a denial of service by causing the allocation of resources without triggering their release. Frequently-affected resources include memory, CPU, disk space, power or battery, etc.

Modes of Introduction:

– Architecture and Design

Likelihood of Exploit: High

 

Related Weaknesses

CWE-404
CWE-404
CWE-404
CWE-404

 

Consequences

Availability: DoS: Resource Consumption (Other)

An attacker that can influence the allocation of resources that are not properly released could deplete the available resource pool and prevent all other processes from accessing the same type of resource.

 

Potential Mitigations

Phase: Requirements

Effectiveness:

Description: 

Phase: Implementation

Effectiveness:

Description: 

It is good practice to be responsible for freeing all resources you allocate and to be consistent with how and where you free resources in a function. If you allocate resources that you intend to free upon completion of the function, you must be sure to free the resources at all exit points for that function including error conditions.

Phase: Operation, Architecture and Design

Effectiveness:

Description: 

CVE References

 

  • CVE-2007-0897
    • 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.
  • CVE-2001-0830
    • Sockets not properly closed when attacker repeatedly connects and disconnects from server.
  • CVE-1999-1127
    • Does not shut down named pipe connections if malformed data is sent.
  • CVE-2009-2858
    • Chain: memory leak (CWE-404) leads to resource exhaustion.
  • CVE-2009-2054
    • Product allows exhaustion of file descriptors when processing a large number of TCP packets.
  • CVE-2008-2122
    • Port scan triggers CPU consumption with processes that attempt to read data from closed sockets.
  • CVE-2007-4103
    • Product allows resource exhaustion via a large number of calls that do not complete a 3-way handshake.
  • CVE-2002-1372
    • Return values of file/socket operations not checked, allowing resultant consumption of file descriptors.
CWE

CWE-771 – Missing Reference to Active Allocated Resource

Read Time:37 Second

Description

The software does not properly maintain a reference to a resource that has been allocated, which prevents the resource from being reclaimed.

This does not necessarily apply in languages or frameworks that automatically perform garbage collection, since the removal of all references may act as a signal that the resource is ready to be reclaimed.

Modes of Introduction:

– Architecture and Design

Likelihood of Exploit: Medium

 

Related Weaknesses

CWE-400

 

Consequences

Availability: DoS: Resource Consumption (Other)

An attacker that can influence the allocation of resources that are not properly maintained could deplete the available resource pool and prevent all other processes from accessing the same type of resource.

 

Potential Mitigations

Phase: Operation, Architecture and Design

Effectiveness:

Description: 

CVE References

 

CWE

CWE-770 – Allocation of Resources Without Limits or Throttling

Read Time:2 Minute, 54 Second

Description

The software allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.

Modes of Introduction:

– Architecture and Design

Likelihood of Exploit: High

 

Related Weaknesses

CWE-400
CWE-665
CWE-400

 

Consequences

Availability: DoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory), DoS: Resource Consumption (Other)

When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource.

 

Potential Mitigations

Phase: Requirements

Effectiveness:

Description: 

Clearly specify the minimum and maximum expectations for capabilities, and dictate which behaviors are acceptable when resource allocation reaches limits.

Phase: Architecture and Design

Effectiveness:

Description: 

Limit the amount of resources that are accessible to unprivileged users. Set per-user limits for resources. Allow the system administrator to define these limits. Be careful to avoid CWE-410.

Phase: Architecture and Design

Effectiveness:

Description: 

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, and it will help the administrator to identify who is committing the abuse. 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: Implementation

Effectiveness:

Description: 

This will only be applicable to cases where user input can influence the size or frequency of resource allocations.

Phase: Architecture and Design

Effectiveness:

Description: 

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Phase: Architecture and Design

Effectiveness:

Description: 

Phase: Architecture and Design

Effectiveness:

Description: 

Ensure that protocols have specific limits of scale placed on them.

Phase: Architecture and Design, Implementation

Effectiveness:

Description: 

Phase: Operation, Architecture and Design

Effectiveness:

Description: 

CVE References

 

  • CVE-2009-4017
    • Language interpreter does not restrict the number of temporary files being created when handling a MIME request with a large number of parts..
  • CVE-2009-2726
    • Driver does not use a maximum width when invoking sscanf style functions, causing stack consumption.
  • CVE-2009-2540
    • Large integer value for a length property in an object causes a large amount of memory allocation.
  • CVE-2009-2054
    • Product allows exhaustion of file descriptors when processing a large number of TCP packets.
  • CVE-2008-5180
    • Communication product allows memory consumption with a large number of SIP requests, which cause many sessions to be created.
  • CVE-2008-1700
    • Product allows attackers to cause a denial of service via a large number of directives, each of which opens a separate window.
  • CVE-2005-4650
    • CMS does not restrict the number of searches that can occur simultaneously, leading to resource exhaustion.
  • CVE-2020-15100
    • web application scanner attempts to read an excessively large file created by a user, causing process termination
CWE

CWE-77 – Improper Neutralization of Special Elements used in a Command (‘Command Injection’)

Read Time:1 Minute, 17 Second

Description

The software constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.

Modes of Introduction:

– Architecture and Design

Likelihood of Exploit: High

 

Related Weaknesses

CWE-74
CWE-74

 

Consequences

Integrity, Confidentiality, Availability: Execute Unauthorized Code or Commands

If a malicious user injects a character (such as a semi-colon) that delimits the end of one command and the beginning of another, it may be possible to then insert an entirely new and unrelated command that was not intended to be executed.

 

Potential Mitigations

Phase: Architecture and Design

Effectiveness:

Description: 

If at all possible, use library calls rather than external processes to recreate the desired functionality.

Phase: Implementation

Effectiveness:

Description: 

If possible, ensure that all external commands called from the program are statically created.

Phase: Implementation

Effectiveness:

Description: 

Phase: Operation

Effectiveness:

Description: 

Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.

Phase: System Configuration

Effectiveness:

Description: 

Assign permissions to the software system that prevents the user from accessing/opening privileged files.

CVE References

 

  • CVE-1999-0067
    • Canonical example of OS command injection. CGI program does not neutralize “|” metacharacter when invoking a phonebook program.
  • CVE-2019-12921
    • image program allows injection of commands in “Magick Vector Graphics (MVG)” language.
  • CVE-2020-11698
    • anti-spam product allows injection of SNMP commands into confiuration file
CWE

CWE-768 – Incorrect Short Circuit Evaluation

Read Time:43 Second

Description

The software contains a conditional statement with multiple logical expressions in which one of the non-leading expressions may produce side effects. This may lead to an unexpected state in the program after the execution of the conditional, because short-circuiting logic may prevent the side effects from occurring.

Modes of Introduction:

– Implementation

Likelihood of Exploit: Low

 

Related Weaknesses

CWE-691

 

Consequences

Confidentiality, Integrity, Availability:

Widely varied consequences are possible if an attacker is aware of an unexpected state in the software after a conditional. It may lead to information exposure, a system crash, or even complete attacker control of the system.

 

Potential Mitigations

Phase: Implementation

Effectiveness:

Description: 

Minimizing the number of statements in a conditional that produce side effects will help to prevent the likelihood of short circuit evaluation to alter control flow in an unexpected way.

CVE References

 

CWE

CWE-767 – Access to Critical Private Variable via Public Method

Read Time:39 Second

Description

The software defines a public method that reads or modifies a private variable.

If an attacker modifies the variable to contain unexpected values, this could violate assumptions from other parts of the code. Additionally, if an attacker can read the private variable, it may expose sensitive information or make it easier to launch further attacks.

Modes of Introduction:

– Architecture and Design

Likelihood of Exploit:

 

Related Weaknesses

CWE-668

 

Consequences

Integrity, Other: Modify Application Data, Other

 

Potential Mitigations

Phase: Implementation

Effectiveness:

Description: 

Use class accessor and mutator methods appropriately. Perform validation when accepting data from a public method that is intended to modify a critical private variable. Also be sure that appropriate access controls are being applied when a public method interfaces with critical data.

CVE References

 

CWE

CWE-766 – Critical Data Element Declared Public

Read Time:38 Second

Description

The software declares a critical variable, field, or member to be public when intended security policy requires it to be private.

Modes of Introduction:

– Architecture and Design

Likelihood of Exploit:

 

Related Weaknesses

CWE-1061

 

Consequences

Integrity, Confidentiality: Read Application Data, Modify Application Data

Making a critical variable public allows anyone with access to the object in which the variable is contained to alter or read the value.

Other: Reduce Maintainability

 

Potential Mitigations

Phase: Implementation

Effectiveness:

Description: 

Data should be private, static, and final whenever possible. This will assure that your code is protected by instantiating early, preventing access, and preventing tampering.

CVE References

 

  • CVE-2010-3860
    • variables declared public allows remote read of system properties such as user name and home directory.
CWE

CWE-765 – Multiple Unlocks of a Critical Resource

Read Time:1 Minute, 5 Second

Description

The software unlocks a critical resource more times than intended, leading to an unexpected state in the system.

When software is operating in a concurrent environment and repeatedly unlocks a critical resource, the consequences will vary based on the type of lock, the lock’s implementation, and the resource being protected. In some situations such as with semaphores, the resources are pooled and extra calls to unlock will increase the count for the number of available resources, likely resulting in a crash or unpredictable behavior when the system nears capacity.

Modes of Introduction:

– Implementation

Likelihood of Exploit:

 

Related Weaknesses

CWE-667
CWE-675

 

Consequences

Availability, Integrity: DoS: Crash, Exit, or Restart, Modify Memory, Unexpected State

 

Potential Mitigations

Phase: Implementation

Effectiveness:

Description: 

When locking and unlocking a resource, try to be sure that all control paths through the code in which the resource is locked one or more times correspond to exactly as many unlocks. If the software acquires a lock and then determines it is not able to perform its intended behavior, be sure to release the lock(s) before waiting for conditions to improve. Reacquire the lock(s) before trying again.

CVE References

 

  • CVE-2009-0935
    • Attacker provides invalid address to a memory-reading function, causing a mutex to be unlocked twice
CWE

CWE-764 – Multiple Locks of a Critical Resource

Read Time:1 Minute, 15 Second

Description

The software locks a critical resource more times than intended, leading to an unexpected state in the system.

When software is operating in a concurrent environment and repeatedly locks a critical resource, the consequences will vary based on the type of lock, the lock’s implementation, and the resource being protected. In some situations such as with semaphores, the resources are pooled and extra locking calls will reduce the size of the total available pool, possibly leading to degraded performance or a denial of service. If this can be triggered by an attacker, it will be similar to an unrestricted lock (CWE-412). In the context of a binary lock, it is likely that any duplicate locking attempts will never succeed since the lock is already held and progress may not be possible.

Modes of Introduction:

– Architecture and Design

Likelihood of Exploit:

 

Related Weaknesses

CWE-667
CWE-675
CWE-662
CWE-662

 

Consequences

Availability, Integrity: DoS: Resource Consumption (CPU), DoS: Crash, Exit, or Restart, Unexpected State

 

Potential Mitigations

Phase: Implementation

Effectiveness:

Description: 

When locking and unlocking a resource, try to be sure that all control paths through the code in which the resource is locked one or more times correspond to exactly as many unlocks. If the software acquires a lock and then determines it is not able to perform its intended behavior, be sure to release the lock(s) before waiting for conditions to improve. Reacquire the lock(s) before trying again.

CVE References

 

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