Mpdavis
CVE-2026-120459: python-jose through 3.5.0 contains an authentication bypass vulnerability that allows unauthenticated attackers to forge JWTs because HMACKey and CryptographyHM
CVE-2026-120459 Nov 2, 2026 Source: Vendor
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.
Source of record
The credited names below are quoted verbatim from the vendor's own advisory:
https://nvd.nist.gov/vuln/detail/CVE-2026-120459
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CVE-2026-120459
BR2026-0000-041196
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Credited as Gavin Blacklock
CVE-2026-120459
BR2026-0000-041197
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Credited as Conner Webber