Vulnerability-Lookup

FKIE_CVE-2026-33036

Vulnerability from fkie_nvd - Published: 2026-03-20 06:16 - Updated: 2026-03-23 16:28

Severity ?

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

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

URL	Tags
security-advisories@github.com	https://github.com/NaturalIntelligence/fast-xml-parser/commit/bd26122c838e6a55e7d7ac49b4ccc01a49999a01	Patch
security-advisories@github.com	https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.5.6	Product, Release Notes
security-advisories@github.com	https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8gc5-j5rx-235r	Exploit, Mitigation, Vendor Advisory

Impacted products

Vendor	Product	Version
naturalintelligence	fast-xml-parser	*
naturalintelligence	fast-xml-parser	4.0.0
naturalintelligence	fast-xml-parser	4.0.0
naturalintelligence	fast-xml-parser	4.0.0
naturalintelligence	fast-xml-parser	4.0.0
naturalintelligence	fast-xml-parser	4.0.0
naturalintelligence	fast-xml-parser	4.0.0
naturalintelligence	fast-xml-parser	4.0.0

JSON

To clipboard

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      "value": "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 (\u0026#NNN;, \u0026#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 \u0026#65; can force ~147MB of memory allocation and heavy CPU usage, potentially crashing the process\u2014even when developers have configured strict limits. This issue has been fixed in version 5.5.6."
    },
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    }
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  "lastModified": "2026-03-23T16:28:10.930",
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          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
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          "userInteraction": "NONE",
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  "vulnStatus": "Analyzed",
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      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
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  ]
}

CVE-2026-33036 (GCVE-0-2026-33036)

Vulnerability from cvelistv5 – Published: 2026-03-20 05:17 – Updated: 2026-03-25 13:57

Title

fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)

Summary

Severity ?

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-776 - Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

Assigner

GitHub_M

References

URL

Tags

	https://github.com/NaturalIntelligence/fast-xml-p…	x_refsource_CONFIRM
	https://github.com/NaturalIntelligence/fast-xml-p…	x_refsource_MISC
	https://github.com/NaturalIntelligence/fast-xml-p…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	NaturalIntelligence	fast-xml-parser	Affected: >= 4.0.0-beta.3, < 5.5.6

Show details on NVD website

JSON

To clipboard

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Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

FKIE_CVE-2026-33036

CVE-2026-33036 (GCVE-0-2026-33036)

Tags

Sightings

Nomenclature