High severity · published Sep 28, 2026
CVE-2026-102271
PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard
7.4
CVSS
0.2%
EPSS
No
On KEV
Description
PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 12% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PY
pyjwt · jpadilla
>= 2.4.0, < 2.14.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-102271
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-102271
x_refsource_CONFIRM
https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773
x_refsource_MISC
https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499
x_refsource_MISC
https://github.com/jpadilla/pyjwt/releases/tag/2.14.0
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