# CVE-2026-56434: NGINX ngx_http_ssi_module vulnerability

> An unauthenticated attacker with MITM capabilities can trigger a use-after-free in NGINX, causing worker restarts or limited memory modification.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/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:** 15 Jul 2026
- **Updated:** 15 Jul 2026
- **Also known as:** ALPINE-CVE-2026-56434, AZL-92496, BELL-CVE-2026-56434, BIT-nginx-2026-56434, BIT-nginx-gateway-2026-56434, CLSA-2026-1787916225, CLSA-2026-1788337827, CLSA-2026-1788338106, CLSA-2026-1792768371, CLSA-2026-1792768506, DEBIAN-CVE-2026-56434, ECHO-9338-7b65-6a75, GHSA-m73p-xg7q-m8f2, MINI-27xg-6v5c-fjmr, MINI-65cf-7gcf-r8p7, MINI-8m5w-w5x3-3rmf, MINI-fq8q-v527-852w, MINI-vm2g-fhc4-h36c, MINI-x392-627h-h8f5, ROOT-OS-ALPINE-315-CVE-2026-56434, ROOT-OS-ALPINE-320-CVE-2026-56434, ROOT-OS-DEBIAN-11-CVE-2026-56434, UBUNTU-CVE-2026-56434

## What is CVE-2026-56434?

CVE-2026-56434 is a high-severity use after free vulnerability in F5 NGINX Open Source, published on 15 Jul 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_http_ssi_module module. This vulnerability may exist when the Server-Side Includes (SSI), proxy_pass, and proxy_buffering off directives are configured. With this configuration, an unauthenticated attacker with man-in-the-middle (MITM) ability to control responses from an upstream server may be able to cause a use-after-free in the NGINX worker process. This issue may lead to limited modification of memory or a restart of the NGINX worker process.

Impact:
This vulnerability may allow remote attackers to have limited control to modify memory contents or restart the NGINX worker process. There is no control plane exposure; this is a data plane issue only.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-56434?

2 open source packages ship an affected version, including nginx and nginx-gateway. It affects 4 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nginx` | Bitnami | From 0.8.11 | 1.30.4, 1.31.3 |
| `nginx-gateway` | Bitnami | From 0.8.11 | 1.30.4, 1.31.3 |

Products: F5 Nginx Gateway Fabric, F5 Nginx Ingress Controller, F5 Nginx Plus, F5 Waf.

## How do I fix CVE-2026-56434?

Upgrade nginx to a fixed version for your release line: 1.30.4 or 1.31.3.

## Is CVE-2026-56434 being exploited?

There is no known exploitation of CVE-2026-56434 in the wild and no public exploit code.

## Other vulnerabilities in F5 NGINX Open Source

- [CVE-2026-42533](https://insights.sbomify.com/CVE-2026-42533/): NGINX Map directive and Regex matching vulnerability (critical 9.2)
- [CVE-2026-42530](https://insights.sbomify.com/CVE-2026-42530/): NGINX Open-Source ngx_http_v3_module vulnerability (critical 9.2)
- [CVE-2026-60005](https://insights.sbomify.com/CVE-2026-60005/): NGINX ngx_http_slice_module vulnerability (high 8.8)
- [CVE-2026-11311](https://insights.sbomify.com/CVE-2026-11311/): NGINX Gateway Fabric vulnerability (high 8.6)
- [CVE-2026-50107](https://insights.sbomify.com/CVE-2026-50107/): NGINX Gateway Fabric vulnerability (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-56434 and fix it if it is affected.

What it is: CVE-2026-56434 is a high-severity use after free vulnerability in F5 NGINX Open Source, published on 15 Jul 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-2026-56434 in the wild and no public exploit code.

Affected packages and fixed versions:
- nginx (Bitnami): affected from 0.8.11; fixed in 1.30.4, 1.31.3
- nginx-gateway (Bitnami): affected from 0.8.11; fixed in 1.30.4, 1.31.3

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-2026-56434/ (Markdown: https://insights.sbomify.com/CVE-2026-56434/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56434
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56434
- OSV: https://osv.dev/vulnerability/CVE-2026-56434

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-56434/
Summaries are generated and may contain mistakes; the official description above is the record.