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VulnerabilityPublished

CVE-2026-126190: facelessuser soupsieve · Inefficient Algorithmic Complexity

Affects facelessuser soupsieveSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High : upgrade to 4.0 soon.

Data as of 12 Nov 2026, 17:04 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 3.17.5
Patch
Available – fixed in 4.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 12 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
facelessusersoupsieveAffected
  • <4.0
Fixed in
  • 4.0

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

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