CVE-2026-126066
fast-xml-parser: Quadratic CPU consumption scanning unterminated stop-node tags
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Prior to 5.12.0, when the non-default stopNodes option is enabled, readStopNodeData() in OrderedObjParser.js calls readTagExp() for each less-than character in an unterminated stop-node body and repeatedly rescans the remaining input while looking for a closing greater-than character. An attacker who supplies XML containing many tag fragments without a later closing character can cause quadratic rescanning before parsing fails, blocking a Node.js event loop and causing CPU-exhaustion denial of service. This issue is fixed in version 5.12.0.
Fixes and workarounds
Fix
fast-xml-parser (npm): OSV reports a fixed version 5.12.0. Check the advisory for supported release branches.
Source: OSV GHSA-474x-hrwr-fgx4Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| fast-xml-parser NaturalIntelligence |
< 5.12.0 (affected) | CNA: GitHub_M |
fast-xml-parserfast-xml-parser
npm |
≥ 0; < 5.12.0 (affected, semver); OSV events: introduced 0; fixed 5.12.0Source events (semver)Other versions: unaffected |
OSV GHSA-474x-hrwr-fgx4 |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 3.7 low |
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L | CNA: GitHub_M |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-474x-hrwr-fgx4CNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/0c3659348364959da62954b73728fb3bd05ebcb4CNA: GitHub_M · x_refsource_MISC
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.12.0CNA: GitHub_M · x_refsource_MISC
- https://github.com/advisories/GHSA-474x-hrwr-fgx4OSV / GitHub Security Advisories · advisory
- https://osv.dev/vulnerability/GHSA-474x-hrwr-fgx4OSV / GitHub Security Advisories · osv
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