NULL pointer dereference in NGINX Open Source and NGINX Plus - CVE-2026-27651
Published: March 25, 2026
Vulnerability identifier: #VU124473
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-27651
CWE-ID: CWE-476
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: F5 Networks
Affected software:
NGINX Open Source
NGINX Plus
NGINX Open Source
NGINX Plus
Detailed vulnerability description
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to a NULL pointer dereference error within the ngx_mail_auth_http_module module. A remote attacker can send specially crafted request to the server and perform a denial of service (DoS) attack.
Successful exploitation of the vulnerability requires that the CRAM-MD5 or APOP authentication is enabled, and the authentication server permits retry by returning the Auth-Wait response header.
How to mitigate CVE-2026-27651
Install updates from vendor's website.