CVE-2026-126066: NaturalIntelligence fast-xml-parser · Inefficient Algorithmic Complexity
Affects NaturalIntelligence fast-xml-parserSource CVE Database V5
Not known to be exploited · CVSS 3.7 Low : upgrade to 5.12.0 when convenient.
Data as of 10 Nov 2026, 20:36 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 3.1 | 3.7 |
|---|
- Patch
- Available – fixed in 5.12.0
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:LExploitation evidence
Disclosed: evidence found.
CVE published 10 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 10 Nov 2026.
What to do
Upgrade NaturalIntelligence fast-xml-parser to 5.12.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| NaturalIntelligencefast-xml-parser | Affected
| Fixed in
|
AI-suggested
Upgrade fast-xml-parser to version 5.12.0 or later, where this issue is fixed. No other mitigation is required as the vulnerability is resolved in the official patch.
Description
CVE-2026-126066 is a vulnerability in NaturalIntelligence's fast-xml-parser prior to version 5.12.0. When the non-default stopNodes option is enabled, the parser's readStopNodeData() function repeatedly rescans input containing many tag fragments without a closing character, causing quadratic time complexity. This leads to CPU exhaustion and denial of service by blocking the Node.js event loop. The issue is fixed in version 5.12.0.
References
- github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-474x-hrwr-fgx4 (opens in a new tab)
- github.com/NaturalIntelligence/fast-xml-parser/commit/0c3659348364959da62954b73728fb3bd05ebcb4 (opens in a new tab)
- github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.12.0 (opens in a new tab)