CVSS 3.1
3.7 lowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:LCVE-2026-126066 fast-xml-parser: Quadratic CPU consumption scanning unterminated stop-node tags
Low (3.7) in naturalintelligence fast-xml-parser. EPSS 0.5% estimated probability of exploitation activity in the next 30 days. Fixed in fast-xml-parser 5.12.0.
On this page
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.
Severity
- EPSS
- 0.5% estimated probability of exploitation activity in the next 30 days; 40th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- CISA's assessment (SSVC)
- Exploitation: none · Automatable: no · Technical impact: partial, assessed 2026-11-12. From CISA's Vulnrichment in the CVE List: whether it is exploited, whether exploiting it can be automated, and how much control it gives.
- CWE
- CWE-407 Inefficient Algorithmic Complexity
- Published
- Modified
- Assigned by
- GitHub_M (CNA)
- NVD analysis
- Deferred: the NVD does not plan to analyze it
- Record from
- the NVD, synced
Ask an AI about this CVE
Show the prompt
Explain CVE-2026-126066 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-126066?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-126066?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-126066 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.
Badge for a README or a site
An image that stays current: it is drawn from the data each time it is fetched (a host that proxies images, as GitHub does, may show its copy for a while). Markdown:
[](https://cve.bz/cve/CVE-2026-126066)
HTML:
<a href="https://cve.bz/cve/CVE-2026-126066"><img src="https://cve.bz/cve/badge/CVE-2026-126066.svg" alt="CVE-2026-126066"></a>
Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| NaturalIntelligence fast-xml-parser | < 5.12.0 |
Fix and patched versions
fast-xml-parser(npm): fixed in 5.12.0
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-474x-hrwr-fgx4 | npm | fast-xml-parser | <5.12.0 | 5.12.0 |
History
- The NVD deferred its analysis
Changes since this site first stored the record. The same for every record: /api/public/changes.