# CVE-2026-33036

## Summary

- **CVE ID:** CVE-2026-33036
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** CWE-776
- **Published:** Mar 20, 2026
- **Last Modified:** Mar 25, 2026

## Description

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.

## Affected Products

- NaturalIntelligence — fast-xml-parser (>= 4.0.0-beta.3, < 5.5.6)

## References

- [CNA](https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8gc5-j5rx-235r)
- [CNA](https://github.com/NaturalIntelligence/fast-xml-parser/commit/bd26122c838e6a55e7d7ac49b4ccc01a49999a01)
- [CNA](https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.5.6)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.58%
- **EPSS Percentile:** 45.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._