# CVE-2026-27651: NGINX ngx_mail_auth_http_module vulnerability

> Attackers can crash NGINX worker processes via crafted requests when mail authentication with retry support is enabled.

- **Severity:** High 8.7 (`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`)
- **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:** 15 Jul 2026
- **Also known as:** ALPINE-CVE-2026-27651, AZL-80771, BELL-CVE-2026-27651, BIT-nginx-2026-27651, BIT-nginx-gateway-2026-27651, DEBIAN-CVE-2026-27651, ECHO-a09e-6ba8-3be0, GHSA-82w2-x7hf-5h8r, MINI-8g74-hv79-vmpg, MINI-ghjj-p693-crrw, MINI-p6rr-wm44-95fx, MINI-w59p-554p-455v, ROOT-OS-ALPINE-315-CVE-2026-27651, ROOT-OS-ALPINE-320-CVE-2026-27651, ROOT-OS-ALPINE-321-CVE-2026-27651, UBUNTU-CVE-2026-27651

## What is CVE-2026-27651?

CVE-2026-27651 is a high-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

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.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-27651?

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 0.5.15 | 1.28.3, 1.29.7 |
| `nginx-gateway` | Bitnami | From 0.5.15 | 1.28.3, 1.29.7 |

Products: F5 Nginx Open Source, F5 Nginx Plus.

## How do I fix CVE-2026-27651?

Upgrade nginx to a fixed version for your release line: 1.28.3 or 1.29.7.

## Is CVE-2026-27651 being exploited?

There is no known exploitation of CVE-2026-27651 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-2026-27784](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)
- [CVE-2024-24990](https://insights.sbomify.com/CVE-2024-24990/): NGINX HTTP/3 QUIC vulnerability (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27651 and fix it if it is affected.

What it is: CVE-2026-27651 is a high-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-2026-27651 in the wild and no public exploit code.

Affected packages and fixed versions:
- nginx (Bitnami): affected from 0.5.15; fixed in 1.28.3, 1.29.7
- nginx-gateway (Bitnami): affected from 0.5.15; 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-2026-27651/ (Markdown: https://insights.sbomify.com/CVE-2026-27651/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27651
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27651
- OSV: https://osv.dev/vulnerability/CVE-2026-27651

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27651/
Summaries are generated and may contain mistakes; the official description above is the record.