CVE-2026-126190: Soup Sieve · Polynomial-time denial of service in the descendant combinator
Affects soupsieveSource GCVE Database
Not known to be exploited · CVSS 7.5 High : upgrade to 4.0.0 soon.
Data as of 13 Nov 2026, 01:09 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 3.1 | 7.5 |
|---|
- Patch
- Available – fixed in 4.0.0
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 soupsieve to 4.0.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| PyPIsoupsieve | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Upgrade to Soup Sieve version 4.0.0 or later, where the vulnerability is fixed by caching ancestor match results to ensure linear-time selector matching. No code changes are needed beyond upgrading. If upgrading is not possible, reduce the use of descendant combinators in selectors on untrusted input, limit the size and nesting depth of untrusted documents, or run selector operations with time limits in isolated worker processes. Avoid using the NOCACHE flag as it disables caching and reintroduces the vulnerability.
Description
Soup Sieve versions prior to 4.0.0 contain a polynomial-time denial of service vulnerability in the descendant combinator selector matching. The time complexity grows polynomially with the nesting depth of the document and the number of descendant combinators in the selector, allowing an attacker controlling input HTML or XML to cause high CPU usage by submitting deeply nested documents. This can lead to significant delays or denial of service in applications using Soup Sieve to process untrusted markup. The issue is fixed in version 4.0.0 by introducing caching to reduce matching time to linear complexity.
References
- github.com/facelessuser/soupsieve/security/advisories/GHSA-mmhr-3c5m-f64f (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-126190 (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 (opens in a new tab)
- github.com/facelessuser/soupsieve/releases/tag/4.0 (opens in a new tab)