fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB of memory allocation and heavy CPU usage, potentially crashing the process—even when developers have configured strict limits. This issue has been fixed in version 5.5.6.
References
| Link | Resource |
|---|---|
| https://github.com/NaturalIntelligence/fast-xml-parser/commit/bd26122c838e6a55e7d7ac49b4ccc01a49999a01 | Patch |
| https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.5.6 | Product Release Notes |
| https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8gc5-j5rx-235r | Exploit Mitigation Vendor Advisory |
Configurations
Configuration 1 (hide)
|
History
No history.
Information
Published : 2026-03-20 06:16
Updated : 2026-03-23 16:28
NVD link : CVE-2026-33036
Mitre link : CVE-2026-33036
CVE.ORG link : CVE-2026-33036
JSON object : View
Products Affected
naturalintelligence
- fast-xml-parser
CWE
CWE-776
Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')