CWE-768: Incorrect Short Circuit Evaluation

How it's found

Incorrect Short Circuit Evaluation is a specific, narrowly defined instance of a broader pattern. Testers confirm it with targeted code review and a proof-of-concept input that exercises the exact code path this weakness describes.

Usage of short circuit evaluation, though well-defined in the C standard, may alter control flow in a way that introduces logic errors that are difficult to detect, possibly causing errors later during the product's execution. If an attacker can discover such an inconsistency, it may be exploitable to gain arbitrary control over a system. If the first condition of an "or" statement is assumed to be true under normal circumstances, or if the first condition of an "and" statement is assumed to be false, then any subsequent conditional may contain its own logic errors that are not detected during code review or testing. Finally, the usage of short circuit evaluation may decrease the maintainability of the code.

Consequences

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

Mitigations

• Implementation: 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.

Where this fits in a TurboPentest engagement

This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.

Frequently asked questions

Related CWEs

• Pillar weakness
  CWE-691: Insufficient Control Flow Management