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Vulnerabilities

Vulnerability · CVE-2026-26278

fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback.

Published Feb 19, 2026 · catalog updated Sep 10, 2026 · NaturalIntelligence

Last checked Nov 12, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-26278. EPSS is 0.94%. Act only if a listed version of NaturalIntelligence is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.94%
Remediation
Version ranges on file
Affected products
vendor NaturalIntelligence fast-xml-parser 5.0.0, < 5.3.6

fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the application. Version 5.3.6 fixes the issue. As a workaround, avoid using DOCTYPE parsing by option.

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.

  • vendor NaturalIntelligence fast-xml-parser 5.0.0, < 5.3.65.0.0, < 5.3.6

How to fix CVE-2026-26278

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-2026-26278. EPSS is 0.94%. Act only if a listed version of NaturalIntelligence is installed.

Which versions are affected?

Compare what you have installed with NaturalIntelligence fast-xml-parser 5.0.0, < 5.3.6 5.0.0, < 5.3.6. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.94%. 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. Feb 19, 2026 · EUVD

    Detected

    fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the

  2. Sep 10, 2026 · EUVD

    Updated

    fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the

Sources

  • CVE.orgVulnerability recordCVE-2026-26278

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-26278

    30-day exploitation probability 0.94%

    first.org
  • EUVDVulnerability recordEUVD-2026-7970

    fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML inpu

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 12, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 9, 2026
  • CVE.orgNov 6, 2026
  • EUVDNov 5, 2026