NGINX
CVE-2026-28753: NGINX ngx_mail_proxy_module vulnerability
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_mail_smtp_module module due to the improper handling of CRLF sequences in DNS responses.
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 0.6 | 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
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_mail_smtp_module module due to the improper handling of CRLF sequences in DNS responses. This allows an attacker-controlled DNS server to inject arbitrary headers into SMTP upstream requests, leading to potential request manipulation. 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.