Insufficient verification of data authenticity in pyjwt - #VU151960
Published: September 24, 2026
Vulnerability identifier: #VU151960
CSH Severity: Medium
CVSS v4: 8.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-345
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to use a stolen sender-constrained access token without possessing the legitimate holder's private key.
The vulnerability exists due to insufficient verification of data authenticity in OKP private JWK import handling in jwt/algorithms.py when processing a JWK whose x and d values belong to different key pairs. A remote attacker can supply a crafted private OKP JWK to use a stolen sender-constrained access token without possessing the legitimate holder's private key.
Exploitation requires a DPoP verifier that calculates a thumbprint from x, passes the complete JWK to PyJWT for signature verification, and does not reject private JWK parameters.
Affected software
pyjwt
Remediation
Install security update from vendor's website.
pyjwt - update to 2.15.0