CVE-2026-33036
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| sles | affected | | |
| debian | bookworm | undetermined | |
| debian | forky | undetermined | |
| debian | sid | undetermined | |
| debian | trixie | undetermined | |
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| npm | fast-xml-parser | >=5.0.0,<5.5.6 | 5.5.6 |
| npm | fast-xml-parser | >=4.0.0-beta.3,<4.5.5 | 4.5.5 |
References
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8gc5-j5rx-235r
- https://nvd.nist.gov/vuln/detail/CVE-2026-33036
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/bd26122c838e6a55e7d7ac49b4ccc01a49999a01
- https://github.com/NaturalIntelligence/fast-xml-parser
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v4.5.5
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.5.6
- https://www.suse.com/security/cve/CVE-2026-33036.html
- https://security-tracker.debian.org/tracker/CVE-2026-33036
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.