CWE-777: Regular Expression without Anchors
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.
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Overview
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.
Background
Regular expressions are typically used to match a pattern of text. Anchors are used in regular expressions to specify where the pattern should match: at the beginning, the end, or both (the whole input).
Real-world CVEs
1 recorded CVEs are caused by CWE-777 (Regular Expression without Anchors). The highest-severity and most recent are shown first. 1 new CWE-777 CVE has been recorded so far in 2026.
Common consequences
What can happen when CWE-777 is exploited.
Bypass Protection Mechanism
Affects: Availability, Confidentiality, Access Control
An unanchored regular expression in the context of an allowlist will possibly result in a protection mechanism failure, allowing malicious or malformed data to enter trusted regions of the program. The specific consequences will depend on what functionality the allowlist was protecting.