CWE-367
Time-of-check Time-of-use (TOCTOU) Race Condition
AI Translation Available
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
Status
incomplete
Abstraction
base
Likelihood
medium
Affected Platforms
Technical Details
AI Translation
Common Consequences
integrity
other
non-repudiation
Impacts
alter execution logic
unexpected state
modify application data
modify files or directories
modify memory
other
hide activities
Detection Methods
automated static analysis
Potential Mitigations
Phases:
implementation
architecture and design
Descriptions:
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When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
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The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
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Limit the interleaving of operations on files from multiple processes.
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Recheck the resource after the use call to verify that the action was taken appropriately.
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If you cannot perform operations atomically and you must share access to the resource between multiple processes or threads, then try to limit the amount of time (CPU cycles) between the check and use of the resource. This will not fix the problem, but it could make it more difficult for an attack to succeed.
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Ensure that some environmental locking mechanism can be used to protect resources effectively.
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Ensure that locking occurs before the check, as opposed to afterwards, such that the resource, as checked, is the same as it is when in use.