CVE-2026-126190

Soup Sieve: Polynomial-time denial of service in the descendant combinator

Published Nov 12, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-mmhr-3c5m-f64f Soup Sieve: Polynomial-time denial of service in the descendant combinator
History
Type Values Removed Values Added
First Time appeared Facelessuser
Facelessuser soupsieve
Vendors & Products Facelessuser
Facelessuser soupsieve
Type Values Removed Values Added
Description 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.
Title Soup Sieve: Polynomial-time denial of service in the descendant combinator
Weaknesses CWE-407
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Nov 12, 2026, 4:54 PM
Reserved
Nov 10, 2026, 8:07 PM
Status
Awaiting Analysis
Published
Nov 12, 2026, 5:17 PM
Modified
Nov 12, 2026, 7:09 PM