NGINX
CVE-2026-27651: NGINX ngx_mail_auth_http_module vulnerability
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.
Published
Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.
Affected and fixed versions
| Product / branch | Fixed in |
|---|---|
| NGINX Open Source 1.29 | 1.29.7 or later |
| NGINX Open Source 0.5 | 1.28.3 or later |
| NGINX Plus R36 | R36 P3 or later |
| NGINX Plus R35 | R35 P2 or later |
| NGINX Plus R34 | * or later |
| NGINX Plus R33 | * or later |
| NGINX Plus R32 | R32 P5 or later |
Always confirm against the vendor advisory, which lists every fixed hotfix.
What it is
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.
Sources
KEV status, EPSS score and vendor data refreshed automatically, last on 12 Oct 2026.