CVE-2026-26278
fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)
- State
- Published
- Severity
- 7.5 High
- Published
- Feb 19, 2026
- Updated
- Sep 10, 2026
- Reserved
- Feb 12, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | GitHub_M |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | redhat-SADP |
Weaknesses
- CWE-776 Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Affected Products
| Product | Versions |
|---|---|
fast-xml-parserNaturalIntelligence |
|
References
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jmr7-xgp7-cmfj
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/910dae5be2de2955e968558fadf6e8f74f117a77
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.6
- https://access.redhat.com/security/cve/CVE-2026-26278vdb-entry
- RHBZ#2441120issue-tracking
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26278.json
- https://access.redhat.com/errata/RHSA-2026:7110vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:7128vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:6174vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:6802vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:41941vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:41944vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:40984vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:51349vendor-advisory
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