CVE-2026-126190: facelessuser soupsieve · Inefficient Algorithmic Complexity
Affects facelessuser soupsieveSource CVE Database V5
Not known to be exploited · CVSS 7.5 High : upgrade to 4.0 soon.
Data as of 12 Nov 2026, 17:04 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 3.1 | 7.5 |
|---|
- Patch
- Available – fixed in 4.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 12 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 12 Nov 2026.
What to do
Upgrade facelessuser soupsieve to 4.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| facelessusersoupsieve | Affected
| Fixed in
|
AI-suggested
Upgrade to Soup Sieve version 4.0 or later, where this inefficiency is fixed. Avoid using selectors compiled with the NOCACHE option against untrusted documents, as they retain the vulnerable behavior.
Description
CVE-2026-126190 is a high-severity vulnerability in the Soup Sieve CSS selector library used with Beautiful Soup 4. Versions prior to 4.0 suffer from inefficient algorithmic complexity when processing descendant combinators in CSS selectors, causing repeated ancestor walks that increase polynomially with nesting depth. This can lead to significant CPU resource consumption and prolonged worker occupation when processing untrusted HTML or XML documents. The issue is resolved in version 4.0.
References
- github.com/facelessuser/soupsieve/security/advisories/GHSA-mmhr-3c5m-f64f (opens in a new tab)
- github.com/facelessuser/soupsieve/pull/351 (opens in a new tab)
- github.com/facelessuser/soupsieve/commit/ff1a5ce7e5addc31626d7b6053511fecdb4f6320 (opens in a new tab)
- github.com/facelessuser/soupsieve/releases/tag/4.0 (opens in a new tab)