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Vulnerabilities

Vulnerability · CVE-2026-33036

fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks.

Published Mar 20, 2026 · catalog updated Jun 17, 2026 · Red Hat

Check if you run it

No confirmed exploitation is on record for CVE-2026-33036. EPSS is 0.76%. Act only if a listed version of Red Hat is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.76%
Remediation
Advisory link
Affected products
cpe naturalintelligence/fast-xml-parser

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe naturalintelligence/fast-xml-parser4.0.0

How to fix CVE-2026-33036

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-33036. EPSS is 0.76%. Act only if a listed version of Red Hat is installed.

Which versions are affected?

Compare what you have installed with 4.0.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-776. EPSS 0.76%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 20, 2026 · NIST NVD

    Detected

    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 De

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 De

Sources

  • CSAF AdvisoriesVendor advisoryRHSA-2026:9742:CVE-2026-33036

    A flaw was found in fast-xml-parser. A remote attacker can exploit this vulnerability by supplying specially crafted XML input containing numeric character references or standard XML entities. This input can bypass configured entity expansion limits, leading to excessive memory a

    security.access.redhat.com
  • CVE.orgVulnerability recordCVE-2026-33036

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-33036

    30-day exploitation probability 0.8%

    first.org
  • NIST NVDVulnerability recordCVE-2026-33036

    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 expa

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.