CVE-2026-102271
PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard
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.
INFO
Published Date :
Sept. 28, 2026, 9:17 p.m.
Last Modified :
Oct. 6, 2026, 6:36 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update PyJWT to version 2.14.0 or later.
- Ensure DER public keys are not used as HMAC secrets.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-102271.
| URL | Resource |
|---|---|
| https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499 | Patch |
| https://github.com/jpadilla/pyjwt/releases/tag/2.14.0 | Product Release Notes |
| https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773 | Exploit Patch Vendor Advisory |
| https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773 | Exploit Patch Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-102271 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-102271
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-102271 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-102271 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Oct. 06, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:* versions from (including) 2.4.0 up to (excluding) 2.14.0 Added Reference Type GitHub, Inc.: https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/jpadilla/pyjwt/releases/tag/2.14.0 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773 Types: Exploit, Patch, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773 Types: Exploit, Patch, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Oct. 01, 2026
Action Type Old Value New Value Added Reference https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773 Added SSVC {'id': 'CVE-2026-102271', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-10-01T14:57:03.181101Z'} -
New CVE Received by [email protected]
Sep. 28, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N Added CWE CWE-347 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/102xxx/CVE-2026-102271.json">CVE-2026-102271</a> Added Reference https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499 Added Reference https://github.com/jpadilla/pyjwt/releases/tag/2.14.0 Added Reference https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773