# 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.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Mar 2026
- **Updated:** 24 Mar 2026
- **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, ECHO-c2a8-5145-c36a, GHSA-ggr6-fmr8-2m8g, MINI-5r9w-mm8w-j4cp, MINI-7gvr-mgj8-5mh9, MINI-fpfx-x5rv-x555, MINI-vr4h-4hf4-f575, UBUNTU-CVE-2026-28753

## 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 (Improper Neutralization of CRLF Sequences)

## 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 | Ecosystem | 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: 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

- [CVE-2026-27654](https://insights.sbomify.com/CVE-2026-27654/): NGINX ngx_http_dav_module vulnerability (high 8.8)
- [CVE-2026-27651](https://insights.sbomify.com/CVE-2026-27651/): NGINX ngx_mail_auth_http_module vulnerability (high 8.7)
- [CVE-2026-27784](https://insights.sbomify.com/CVE-2026-27784/): NGINX ngx_http_mp4_module vulnerability (high 8.5)
- [CVE-2026-32647](https://insights.sbomify.com/CVE-2026-32647/): NGINX ngx_http_mp4_module vulnerability (high 8.5)
- [CVE-2024-24989](https://insights.sbomify.com/CVE-2024-24989/): NGINX HTTP/3 QUIC vulnerability (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-28753 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-28753 in the wild and no public exploit code.

Affected packages and fixed versions:
- nginx (Bitnami): affected from 0.6.27; fixed in 1.28.3, 1.29.7
- nginx-gateway (Bitnami): affected from 0.6.27; fixed in 1.28.3, 1.29.7

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-28753/ (Markdown: https://insights.sbomify.com/CVE-2026-28753/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28753
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28753
- OSV: https://osv.dev/vulnerability/CVE-2026-28753

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-28753/
Summaries are generated and may contain mistakes; the official description above is the record.