NULL pointer dereference in lua-resty-jwt - #VU163204
Published: November 9, 2026
Vulnerability identifier: #VU163204
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-476
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows an unauthenticated remote attacker to crash nginx worker processes and cause sustained denial of service.
The vulnerability exists due to a NULL pointer dereference in the lua-resty-jwt OpenSSL FFI layer when verifying an ECDSA JWT using an RSA public key or certificate without algorithm restrictions from jwt:set_alg_whitelist. An unauthenticated remote attacker can repeatedly submit JWTs specifying an ECDSA algorithm with correctly sized signatures to keep workers crashing.
Affected software
lua-resty-jwt
Remediation
Install security update from vendor's website.
lua-resty-jwt - update to 0.4.0