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CVE-2026-120459

9.1 criticalEPSS 0.3%

Critical (9.1). EPSS 0.3% estimated probability of exploitation activity in the next 30 days.

On this page
python-jose through 3.5.0 contains an authentication bypass vulnerability that allows unauthenticated attackers to forge JWTs because HMACKey and CryptographyHMACKey accept zero-length HMAC secrets. When an application's HS256/HS384/HS512 verification key resolves to empty, such as an oct JWK with empty k, attackers can forge tokens with arbitrary claims that jwt.decode accepts.

Severity

CVSS 4.0

9.1 critical
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS 3.1

7.4 high
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS
0.3% estimated probability of exploitation activity in the next 30 days; 17th percentile. Scored 2026-11-05. A forecast for this CVE across the internet, not for your own systems.
CWE
CWE-347 Improper Verification of Cryptographic Signature
OWASP Top 10
A04:2025 Cryptographic Failures
Published
Modified
Record from
the NVD, synced

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Linux distributions

DistributionReleasePackageFixed inAdvisory
Ubuntu22.04:LTS, 24.04:LTSpython-joseno fix listedUBUNTU-CVE-2026-120459

From the distributions' data via OSV.dev: Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Ubuntu.

Attack patterns (CAPEC)

  • CAPEC-463 Padding Oracle Crypto Attack Severity: High
  • CAPEC-475 Signature Spoofing by Improper Validation Likelihood: Low · Severity: High

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.

References

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