CVE-2026-102266 PyJWT - Authentication Bypass

PyJWT 2.13.0 to < 2.14.0 contains a broken authentication caused by missing prepare_key validation in HMACAlgorithm.from_jwk, letting attackers forge HMAC tokens with zero-length keys, exploit requires crafted JWK Set with empty key.

CVSS base score 7.4 /10
High
CISA KEV
Not listed
Public exploit
Proof of concept available
EPSS
0.18% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Broken Authentication
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
28 September 2026
Updated
15 October 2026
Weakness
CWE-347

Vendor fix

Upgrade to version 2.14.0 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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