CWE-777: Regular Expression without Anchors

MITRE CWE weakness

Description

The product uses a regular expression to perform neutralization, but the regular expression is not anchored and may allow malicious or malformed data to slip through.

When performing tasks such as validating against a set of allowed inputs (allowlist), data is examined and possibly modified to ensure that it is well-formed and adheres to a list of safe values. If the regular expression is not anchored, malicious or malformed data may be included before or after any string matching the regular expression. The type of malicious data that is allowed will depend on the context of the application and which anchors are omitted from the regular expression.

Common consequences

• Availability, Confidentiality, Access Control: Bypass Protection Mechanism

Mitigations

Implementation — Be sure to understand both what will be matched and what will not be matched by a regular expression. Anchoring the ends of the expression will allow the programmer to define an allowlist strictly limited to what is matched by the text in the regular expression. If you are using a package that only matches one line by default, ensure that you can match multi-line inputs if necessary.

References

• CWE page: https://cwe.mitre.org/data/definitions/777.html
• CWE list: https://cwe.mitre.org/data/index.html