CVE-2026-26278
fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-776 |
| Vendor | naturalintelligence |
| Product | fast-xml-parser |
| Published | Feb 19, 2026 |
| Last Updated | Mar 2, 2026 |
Stay Ahead of the Next One
Get instant alerts for naturalintelligence fast-xml-parser
Be the first to know when new high vulnerabilities affecting naturalintelligence fast-xml-parser are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
NaturalIntelligence / fast-xml-parser
>= 5.0.0, < 5.3.6 >= 4.1.3, < 4.5.4
References
github.com: https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jmr7-xgp7-cmfj github.com: https://github.com/NaturalIntelligence/fast-xml-parser/commit/910dae5be2de2955e968558fadf6e8f74f117a77 github.com: https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.6