Heap-based buffer overflow in JavaScript module for NGINX - CVE-2026-8711
Published: May 20, 2026
Vulnerability identifier: #VU131922
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-8711
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: F5 Networks
Affected software:
JavaScript module for NGINX
JavaScript module for NGINX
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service or execute arbitrary code.
The vulnerability exists due to heap-based buffer overflow in the ngx_http_js_module module when processing crafted HTTP requests that reach a location invoking ngx.fetch() with the js_fetch_proxy directive configured with at least one client-controlled NGINX variable. A remote attacker can send crafted HTTP requests to cause a denial of service or execute arbitrary code.
Code execution is possible on systems with Address Space Layout Randomization disabled. There is no control plane exposure; this is a data plane issue only.
How to mitigate CVE-2026-8711
Install security update from vendor's website.