Vulnerability-Lookup

UBUNTU-CVE-2026-33036 (CVE-2026-33036)

Vulnerability from osv_ubuntu – Published: 2026-03-20 06:16 – Updated: 2026-05-20 15:27 – Source website

Details

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.

Severity

7.5 (High)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-33036	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-33036	REPORT
	https://github.com/NaturalIntelligence/fast-xml-p…	REPORT
	https://github.com/NaturalIntelligence/fast-xml-p…	REPORT
	https://github.com/NaturalIntelligence/fast-xml-p…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "node-webfont",
            "binary_version": "11.4.0+dfsg2+~cs35.7.26-7ubuntu1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "node-webfont",
        "purl": "pkg:deb/ubuntu/node-webfont@11.4.0+dfsg2+~cs35.7.26-7ubuntu1?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "11.4.0+dfsg2+~cs35.7.26-7ubuntu1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "node-webfont",
            "binary_version": "11.4.0+dfsg2+~cs35.7.26-13ubuntu2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "node-webfont",
        "purl": "pkg:deb/ubuntu/node-webfont@11.4.0+dfsg2+~cs35.7.26-13ubuntu2?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "11.4.0+dfsg2+~cs35.7.26-10",
        "11.4.0+dfsg2+~cs35.7.26-13ubuntu2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "node-webfont",
            "binary_version": "11.4.0+dfsg2+~cs35.7.26-18"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "node-webfont",
        "purl": "pkg:deb/ubuntu/node-webfont@11.4.0+dfsg2+~cs35.7.26-18?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "11.4.0+dfsg2+~cs35.7.26-13ubuntu2",
        "11.4.0+dfsg2+~cs35.7.26-14",
        "11.4.0+dfsg2+~cs35.7.26-15",
        "11.4.0+dfsg2+~cs35.7.26-16build1",
        "11.4.0+dfsg2+~cs35.7.26-18"
      ]
    }
  ],
  "aliases": [],
  "details": "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.",
  "id": "UBUNTU-CVE-2026-33036",
  "modified": "2026-05-20T15:27:21Z",
  "published": "2026-03-20T06:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-33036"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-33036"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8gc5-j5rx-235r"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/NaturalIntelligence/fast-xml-parser/commit/bd26122c838e6a55e7d7ac49b4ccc01a49999a01"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.5.6"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-33036"
  ]
}

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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-03-25 13:57 UTC

CWE

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

Assigner

GitHub_M mitre root Scorecard

References

3 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

1 product

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

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-33036",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-03-25T13:57:14.886976Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-03-25T13:57:58.233Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "fast-xml-parser",
          "vendor": "NaturalIntelligence",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 4.0.0-beta.3, \u003c 5.5.6"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-776",
              "description": "CWE-776: Improper Restriction of Recursive Entity References in DTDs (\u0027XML Entity Expansion\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-03-20T05:17:03.290Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8gc5-j5rx-235r",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8gc5-j5rx-235r"
        },
        {
          "name": "https://github.com/NaturalIntelligence/fast-xml-parser/commit/bd26122c838e6a55e7d7ac49b4ccc01a49999a01",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/NaturalIntelligence/fast-xml-parser/commit/bd26122c838e6a55e7d7ac49b4ccc01a49999a01"
        },
        {
          "name": "https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.5.6",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.5.6"
        }
      ],
      "source": {
        "advisory": "GHSA-8gc5-j5rx-235r",
        "discovery": "UNKNOWN"
      },
      "title": "fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-33036",
    "datePublished": "2026-03-20T05:17:03.290Z",
    "dateReserved": "2026-03-17T18:10:50.210Z",
    "dateUpdated": "2026-03-25T13:57:58.233Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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UBUNTU-CVE-2026-33036 (CVE-2026-33036)

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

Tags

Sightings

Nomenclature

Related by attack behaviour