CVE-2026-107724

Status: DeferredHigh (7.4)—

fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.2.4, fast-jwt can classify raw serialized public JWK or JWKS JSON as an HMAC secret because src/crypto.js performDetectPublicKeyAlgorithms treats non-PEM strings as symmetric key material. If HS256 is explicitly allowed or inferred, an attacker who knows the exact serialized public-key bytes can use those bytes as an HMAC key and create a token containing arbitrary claims that createVerifier accepts. Serialization ordering or whitespace differences can prevent exploitation, and applications using supported PEM keys with an asymmetric-only algorithm allowlist are not affected. This issue is fixed in version 6.3.0.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Base score: 7.4

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.22%
Percentile among all scored CVEs: 12
Score date: 10/15/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1190 Exploit Public-Facing Applicationinitial access85 %
Primary impactT1553.006 Code Signing Policy Modificationdefense impairment80 %
Secondary impactT1078 Valid Accountsstealth · persistence · privilege escalation · initial access75 %

Vulnerabilidad en servicio web remoto (fast-jwt) que permite forjar tokens JWT válidos. Atacante remoto sin autenticación puede generar tokens con claims arbitrarios explotando confusión entre claves públicas y simétricas (CWE-347), impactando autenticación.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Privileged Account Management Application Developer Guidance Active Directory Configuration Vulnerability Scanning User Training User Account Management

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Nearform — Fast-jwt^AI

CWEs

CWE-347

References

Raw JSON (NVD)

Show

{
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          "version": "2.0.3",
          "timestamp": "2026-10-09T15:51:21.495223Z"
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          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
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          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
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        "exploitabilityScore": 2.2
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  "published": "2026-10-08T22:17:28.800",
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      "lang": "en",
      "value": "fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.2.4, fast-jwt can classify raw serialized public JWK or JWKS JSON as an HMAC secret because src/crypto.js performDetectPublicKeyAlgorithms treats non-PEM strings as symmetric key material. If HS256 is explicitly allowed or inferred, an attacker who knows the exact serialized public-key bytes can use those bytes as an HMAC key and create a token containing arbitrary claims that createVerifier accepts. Serialization ordering or whitespace differences can prevent exploitation, and applications using supported PEM keys with an asymmetric-only algorithm allowlist are not affected. This issue is fixed in version 6.3.0."
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  "lastModified": "2026-10-09T16:17:23.740",
  "sourceIdentifier": "security-advisories@github.com"
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