CVSS Vector
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
4Description
When the ngx_mail_auth_http_module module is enabled on NGINX Plus or NGINX Open Source, undisclosed requests can cause worker processes to terminate. This issue may occur when (1) CRAM-MD5 or APOP authentication is enabled, and (2) the authentication server permits retry by returning the Auth-Wait response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Analysis
NGINX worker process crashes via null pointer dereference in the mail authentication module when CRAM-MD5 or APOP authentication is configured with retry-enabled backend servers. This denial of service vulnerability affects NGINX Plus and NGINX Open Source with no patch currently available, allowing unauthenticated remote attackers to terminate worker processes and degrade service availability.
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Remediation
Within 24 hours: Identify all NGINX instances with ngx_mail_auth_http_module enabled and document exposure scope. Within 7 days: Implement network segmentation to restrict access to mail proxy services and deploy WAF rules to filter malformed requests targeting authentication endpoints. …
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External POC / Exploit Code
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EUVD-2026-14880