CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCVE-2026-126191 Soup Sieve: Exponential ReDoS in selector compilation via \9-run in CSS_ESCAPES/IDENTIFIER
High (7.5) in facelessuser soupsieve. EPSS 0.4% estimated probability of exploitation activity in the next 30 days. Fixed in soupsieve 3.0.2.
On this page
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.
Severity
- EPSS
- 0.4% estimated probability of exploitation activity in the next 30 days; 38th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- CISA's assessment (SSVC)
- Exploitation: PoC · Automatable: yes · Technical impact: partial, assessed 2026-11-13. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
- CWE
- CWE-1333 Inefficient Regular Expression Complexity
- Published
- Modified
- Assigned by
- GitHub_M (CNA)
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
Ask an AI about this CVE
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Explain CVE-2026-126191 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-126191?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-126191?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-126191 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.
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Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| facelessuser soupsieve | < 3.0 |
Fix and patched versions
soupsieve(PyPI): fixed in 3.0.2
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-6655-6qjp-jx7x | PyPI | soupsieve | <3.0.2 | 3.0.2 |
Linux distributions
| Distribution | Release | Package | Fixed in | Advisory |
|---|---|---|---|---|
| Ubuntu | 20.04:LTS, 22.04:LTS, 24.04:LTS and 2 more | soupsieve | no fix listed | UBUNTU-CVE-2026-126191 |
From the distributions' data via OSV.dev: Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Ubuntu.
Attack patterns (CAPEC)
- CAPEC-492 Regular Expression Exponential Blowup
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.