Weakness (CWE)
CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition
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.
How to prevent it (7 mitigations)
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Implementation
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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Implementation
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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Architecture and Design
Limit the interleaving of operations on files from multiple processes.
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Implementation, Architecture and Design
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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Implementation
Recheck the resource after the use call to verify that the action was taken appropriately.
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Architecture and Design
Ensure that some environmental locking mechanism can be used to protect resources effectively.
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Implementation
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.
Source: MITRE CWE-367
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Critical 9.8
Apache Tomcat: RCE due to TOCTOU issue in JSP compilation
Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability during JSP compilation in Apache Tomcat permits an RCE on case insensitive file systems when the default servlet is enabled for write (non-default configuration). This issue affects Apache Tomcat…
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Critical 9.0
NVIDIA Container Toolkit contains a Time-of-check Time-of-Use (TOCTOU) vulnerability
NVIDIA Container Toolkit 1.16.1 or earlier contains a Time-of-check Time-of-Use (TOCTOU) vulnerability when used with default configuration where a specifically crafted container image may gain access to the host file system. This does not impact use cases wh…
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Critical 9.8CVE-2021-32708 Public exploit
Time-of-check Time-of-use (TOCTOU) Race Condition in league/flysystem
Flysystem is an open source file storage library for PHP. The whitespace normalisation using in 1.x and 2.x removes any unicode whitespace. Under certain specific conditions this could potentially allow a malicious user to execute code remotely. The condition…