Externally Controlled Reference to a Resource in Another Sphere in pyjwt - #VU132102
Published: May 21, 2026
Vulnerability identifier: #VU132102
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: N/A
CWE-ID: CWE-610
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: jpadilla (José Padilla)
Affected software:
pyjwt
pyjwt
Detailed vulnerability description
The vulnerability allows a remote attacker to forge tokens.
The vulnerability exists due to improper restriction of externally controlled reference in PyJWKClient when processing attacker-influenced JKU URLs. A remote attacker can point the JKU URL to an attacker-controlled JWK Set to forge tokens.
This attack chain requires additional application-layer flaws, including attacker write access to the referenced path and untrusted jku derivation.
Remediation
Install security update from vendor's website.