CVE-2026-126190
Soup Sieve: Polynomial-time denial of service in the descendant combinator
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 4.0, Soup Sieve repeatedly walks the same ancestors while matching descendant combinators, and each additional descendant combinator raises the polynomial degree of the work on deeply nested attacker-influenced HTML or XML. Applications using selectors such as section div div through select(), select_one(), or Beautiful Soup CSS APIs against untrusted documents can have a worker occupied for seconds or minutes, while trusted-only document processing is not affected. Selectors compiled with NOCACHE continue to use the old uncached behavior. This issue is fixed in version 4.0.
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 (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 / 7.5 high |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | CNA: GitHub_M |
| 3.1 / 7.5 high |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | 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-mmhr-3c5m-f64fCNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/facelessuser/soupsieve/pull/351CNA: GitHub_M · x_refsource_MISC
- https://github.com/facelessuser/soupsieve/commit/ff1a5ce7e5addc31626d7b6053511fecdb4f6320CNA: GitHub_M · x_refsource_MISC
- https://github.com/facelessuser/soupsieve/releases/tag/4.0CNA: GitHub_M · x_refsource_MISC
- https://github.com/facelessuser/soupsieve/commit/ff1a5ce7e5addc31626d7b6053511fecdb4f6320[email protected]
- https://github.com/facelessuser/soupsieve/pull/351[email protected]
- https://github.com/facelessuser/soupsieve/releases/tag/4.0[email protected]
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-mmhr-3c5m-f64f[email protected]
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