CVE-2026-126191
Received
Received - Intake
Soup Sieve Regex Backtracking DoS Vulnerability
Vulnerability report for CVE-2026-126191, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-11-12
Last updated on: 2026-11-12
Assigner: GitHub, Inc.
Description
Description
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 3.0, the CSS_ESCAPES and IDENTIFIER regular-expression subpatterns can backtrack exponentially on runs of ambiguous digit escapes in an attribute-name or tag position of an otherwise valid selector. The failure occurs during selector compilation through soupsieve.compile() or Beautiful Soup select() before SELECTOR_LIMIT is applied, so an application that accepts untrusted selector strings can have a worker stalled by a short input. This issue is fixed in version 3.0.
CVSS Scores
EPSS Scores
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| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| facelessuser | soupsieve | 3.0 |
| facelessuser | soupsieve | to 3.0 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-1333 | The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential. |
