# CVE-2026-8711: NGINX JavaScript vulnerability

CVE-2026-8711 is fixed in 4 products on 1 platform, first by libnginx-mod-http-js 0.9.4-1ubuntu0.1~esm1, released May 19, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-8711
- Priority: High
- CVSS: 9.8 (Important)
- EPSS: 0.0969
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 19, 2026
- Weakness: Heap-based Buffer Overflow
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-8711

## Description

NGINX JavaScript has a vulnerability when the js_fetch_proxy directive is configured with at least one client-controlled NGINX variable (for example, $http_*, $arg_*, $cookie_*) and a location invoking the ngx.fetch() operation from NGINX JavaScript. An unauthenticated attacker can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR.    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-http-js Ubuntu 26.04.1 LTS (resolute) | 0.9.4-1ubuntu0.1~esm1 | [libnginx-mod-http-js 0.9.4-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libnginx-mod-http-js-0.9.4-1ubuntu0.1-esm1.md) | May 19, 2026 |
| Linux | libnginx-mod-js Debian 14 | 0.9.9-1 | [DEBIAN-CVE-2026-8711](https://patchblox.com/security/data/fix/linux/debian-cve-2026-8711.md) | May 27, 2026 |
| Linux | libnginx-mod-stream-js Ubuntu 26.04.1 LTS (resolute) | 0.9.4-1ubuntu0.1~esm1 | [libnginx-mod-stream-js 0.9.4-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libnginx-mod-stream-js-0.9.4-1ubuntu0.1-esm1.md) | May 19, 2026 |
| Linux | njs Ubuntu 26.04.1 LTS (resolute) | 0.9.4-1ubuntu0.1~esm1 | [njs 0.9.4-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-njs-0.9.4-1ubuntu0.1-esm1.md) | May 19, 2026 |

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Data as of 2026-11-08T13:06:02Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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