# CVE-2026-78689: NGINX ngx_http_js_module vulnerablility

CVE-2026-78689 is fixed in 4 products on 1 platform, first by DEBIAN-CVE-2026-78689, released September 10, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-78689
- Priority: High
- CVSS: 8.1 (Important)
- EPSS: 0.0076
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 2, 2026
- Weakness: Heap-based Buffer Overflow
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78689

## Description

Description   NGINX JavaScript (njs) has a vulnerability in the XML module's namespace prefix list parser, reachable through the xml.exclusiveC14n() method. An unauthenticated remote attacker can trigger it when an affected NGINX configuration passes an externally controlled XML namespace prefix list to that method. Both the njs and the QuickJS (qjs) engines are affected. A crafted prefix list causes an out-of-bounds write past the end of a heap allocation. With the njs engine, which is the engine used when the js_engine directive is absent, this corrupts adjacent objects and crashes the NGINX worker. With the QuickJS engine, the same call additionally leaks the prefix list on every invocation, causing worker memory to grow across requests. The official nginxinc/nginx-saml reference implementation is affected during SAML signature verification. It reads InclusiveNamespaces/@PrefixList from an untrusted SAML message and passes it to xml.exclusiveC14n() before the signature has been verified, so a valid SAML signature is not required. A crafted SAML Response, Assertion, LogoutRequest, or LogoutResponse is sufficient. Code execution has not been demonstrated and cannot be ruled out for all platforms, as the effect of the out-of-bounds write depends on conditions beyond the attacker's control.            Impact   This vulnerability allows remote attackers to cause a denial of service on the NGINX system, either through repeatable worker restarts or through worker memory growth or possibly trigger code execution. 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libnginx-mod-js Debian 14 | 1.0.1-1 | [DEBIAN-CVE-2026-78689](https://patchblox.com/security/data/fix/linux/debian-cve-2026-78689.md) | Sep 10, 2026 |
| Linux | nginx-mod-njs amzn 2023 | 1.0.1-1.amzn2023.0.1 | [ALAS2023-2026-3095](https://patchblox.com/security/data/fix/linux/alas2023-2026-3095.md) | Sep 28, 2026 |
| Linux | nginx-mod-njs-debuginfo amzn 2023 | 1.0.1-1.amzn2023.0.1 | [ALAS2023-2026-3095](https://patchblox.com/security/data/fix/linux/alas2023-2026-3095.md) | Sep 28, 2026 |
| Linux | nginx-mod-njs-debugsource amzn 2023 | 1.0.1-1.amzn2023.0.1 | [ALAS2023-2026-3095](https://patchblox.com/security/data/fix/linux/alas2023-2026-3095.md) | Sep 28, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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