CVE-2026-48523
PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys
Description
PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.
INFO
Published Date :
May 28, 2026, 4:16 p.m.
Last Modified :
June 1, 2026, 5:44 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update PyJWT to version 2.13.0 or later.
- Ensure JWT algorithm verification is properly implemented.
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-2026-48523.
| URL | Resource |
|---|---|
| https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f | Exploit Vendor Advisory |
| https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f | Exploit 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-2026-48523 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-2026-48523
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-2026-48523 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-48523 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.
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Initial Analysis by [email protected]
Jun. 01, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:* versions from (including) 2.9.0 up to (excluding) 2.12.1 Added Reference Type CISA-ADP: https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f Types: Exploit, Vendor Advisory Added Reference Type GitHub, Inc.: https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
May. 28, 2026
Action Type Old Value New Value Added Reference https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f -
New CVE Received by [email protected]
May. 28, 2026
Action Type Old Value New Value Added Description PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0. Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N Added CWE CWE-347 Added Reference https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f