CVE-2026-26278fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback.
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No exploitation reported and no EPSS estimate yet.
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fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the application. Version 5.3.6 fixes the issue. As a workaround, avoid using DOCTYPE parsing by `processEntities: false` option.
- CVSS
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-776
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Sep 10, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
naturalintelligence fast-xml-parser naturalintelligence:fast-xml-parser | from 4.1.3 before 5.3.6 | NVD |
References
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/910dae5be2de2955e968558fadf6e8f74f117a77patch
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.6product, release-notes
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jmr7-xgp7-cmfjexploit, vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:40984
- https://access.redhat.com/errata/RHSA-2026:41941
- https://access.redhat.com/errata/RHSA-2026:41944
- https://access.redhat.com/errata/RHSA-2026:51349
- https://access.redhat.com/errata/RHSA-2026:6174
- https://access.redhat.com/errata/RHSA-2026:6802
- https://access.redhat.com/errata/RHSA-2026:7110
- https://access.redhat.com/errata/RHSA-2026:7128
- https://access.redhat.com/security/cve/CVE-2026-26278
- https://bugzilla.redhat.com/show_bug.cgi?id=2441120
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26278.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.