CVE-2026-102271 PyJWT - Authentication Bypass

PyJWT 2.4.0 to 2.14.0 contains an authentication bypass caused by improper handling of DER-encoded public keys in HMACAlgorithm.prepare_key, letting attackers forge authenticated HMAC tokens when mixing HMAC and asymmetric algorithms, exploit requires attacker knowledge of the public 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

Update 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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