CVE-2026-126189
Soup Sieve: Quadratic-time denial of service when matching `:has()`
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 4.0.1, Soup Sieve repeatedly searches descendant subtrees for each candidate evaluated by :has() and repeatedly reevaluates a parent containing :has(> ...) for each child, causing quadratic matching on deeply nested or wide attacker-influenced HTML or XML. Applications using ordinary fixed selectors through select(), select_one(), or Beautiful Soup CSS APIs against untrusted documents can have a worker occupied for seconds or minutes, while applications that process only trusted documents are not affected. Selectors compiled with NOCACHE continue to use the old uncached behavior. This issue is fixed in version 4.0.1.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| soupsieve facelessuser |
< 4.0.1 (affected) | CNA: GitHub_M |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 5.3 medium |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | CNA: GitHub_M |
| 3.1 / 5.3 medium |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | NVD: [email protected] |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-8jvp-3x96-xpqwCNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/facelessuser/soupsieve/pull/352CNA: GitHub_M · x_refsource_MISC
- https://github.com/facelessuser/soupsieve/commit/0469c148f5501ec2127e0d65b77c2a1c395fa379CNA: GitHub_M · x_refsource_MISC
- https://github.com/facelessuser/soupsieve/commit/305fbf6b8c1f6ff05fec55d1e5bb28d80d22de44CNA: GitHub_M · x_refsource_MISC
- https://github.com/facelessuser/soupsieve/releases/tag/4.0.1CNA: GitHub_M · x_refsource_MISC
- https://github.com/facelessuser/soupsieve/commit/0469c148f5501ec2127e0d65b77c2a1c395fa379[email protected]
- https://github.com/facelessuser/soupsieve/commit/305fbf6b8c1f6ff05fec55d1e5bb28d80d22de44[email protected]
- https://github.com/facelessuser/soupsieve/pull/352[email protected]
- https://github.com/facelessuser/soupsieve/releases/tag/4.0.1[email protected]
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-8jvp-3x96-xpqw[email protected]
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