CVE-2026-28753 NGINX ngx_mail_proxy_module vulnerability
Attacker-controlled DNS servers can inject headers into SMTP requests via NGINX mail proxy, enabling request manipulation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-28753?
CVE-2026-28753 is a medium-severity vulnerability in F5 NGINX Open Source, published on 24 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-93
Which versions are affected by CVE-2026-28753?
2 open source packages ship an affected version, including nginx and nginx-gateway. It affects 2 products.
| Package | Affected | Fixed in |
|---|---|---|
nginx Bitnami | From 0.6.27 | 1.28.3, 1.29.7 |
nginx-gateway Bitnami | From 0.6.27 | 1.28.3, 1.29.7 |
Products include F5 Nginx Open Source, F5 Nginx Plus.
How do I fix CVE-2026-28753?
Upgrade nginx to a fixed version for your release line: 1.28.3 or 1.29.7.
Is CVE-2026-28753 being exploited?
There is no known exploitation of CVE-2026-28753 in the wild and no public exploit code.
Other vulnerabilities in F5 NGINX Open Source
Sources
Also known as ALPINE-CVE-2026-28753, AZL-80780, BELL-CVE-2026-28753, BIT-nginx-2026-28753, BIT-nginx-gateway-2026-28753, DEBIAN-CVE-2026-28753 and 7 more.