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Description

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.

PUBLISHED Reserved 2026-05-30 | Published 2026-07-14 | Updated 2026-07-14 | Assigner GitHub_M




HIGH: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-400: Uncontrolled Resource Consumption

CWE-1333: Inefficient Regular Expression Complexity

Product status

< 2.8.4
affected

References

github.com/...psieve/security/advisories/GHSA-836r-79rf-4m37

github.com/...ommit/eb4397618709186c109400448c6043b728217dc3

github.com/facelessuser/soupsieve/releases/tag/2.8.4

cve.org (CVE-2026-49477)

nvd.nist.gov (CVE-2026-49477)

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