CVE-2026-49477

Summary

Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.8.4, the CSS selector parser in soupsieve contains a regular expression vulnerable to catastrophic backtracking when processing an attribute selector with an unterminated quoted value in soupsieve/css_parser.py, allowing an attacker who can supply untrusted CSS selector strings to soupsieve.compile() or Beautiful Soup .select() / .select_one() to cause CPU exhaustion and denial of service. This issue is fixed in version 2.8.4.

Affected Software

Weaknesses

• CWE-400: CWE-400: Uncontrolled Resource Consumption
• CWE-1333: CWE-1333: Inefficient Regular Expression Complexity

References

• https://github.com/facelessuser/soupsieve/security/advisories/GHSA-836r-79rf-4m37
• https://github.com/facelessuser/soupsieve/commit/eb4397618709186c109400448c6043b728217dc3
• https://github.com/facelessuser/soupsieve/releases/tag/2.8.4

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