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CVE-2026-26278

fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)

No known exploitation. EPSS puts it in the 65th percentile. Fixed in 4.5.4.

CVSS 3.17.5HighEPSS percentile65th1.1% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFix4.5.4Upgrade to this build

Published Updated Sources: CVE.org, NVD, GitHub

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • NaturalIntelligence fast-xml-parserAffected: >= 5.0.0, < 5.3.6Upgrade to: not statedAffected: >= 4.1.3, < 4.5.4Upgrade to: not statedStated by: CVE record
  • Npm Fast-xml-parserAffected: ≥ 4.1.3, < 4.5.4Upgrade to: 4.5.4Stated by: GitHub advisory

Versions as the sources state them. Full version matrix after sign-in

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What it is

From the CVE record

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 `processEntities: false` option.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS65th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

1.1% chance of exploitation activity in the next 30 days, which ranks it in the 65th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

28 events over 203 days, from the signal feeds we watch.

  1. Patch availablerecord updated
  2. Patch availablerecord updated
  3. Patch availablerecord updated
  4. Patch availablerecord updated
  5. Patch availablerecord updated
  6. Patch availablerecord updated

Affected products

And 1 more affected product. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 7.5 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity LowNo special conditions — the attack can be reliably reproduced
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality NoneNo confidentiality impact
  • Integrity NoneNo integrity impact
  • Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Sources

References in the record

And 13 more references. See all after sign-in

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