What is CVE-2026-8711?

CVE-2026-8711 is a high-severity vulnerability in F5 Nginx Javascript, classified under Heap-based Buffer Overflow. CVSS score: 8.1/10. Published 2026-05-19.

How severe is CVE-2026-8711?

High severity. CVSS v3 base score is 8.1 out of 10.

Buffer overflow in F5 Nginx Javascript

CVE-2026-8711

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…

Vulnerability class: Buffer Overflow

EPSS: 0.001 (26.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

F5 Nginx Javascript — versions 0.9.4
F5 Njs

Weakness classification (CWE)

CWE-122 — Heap-based Buffer Overflow

References

f5sirt@f5.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-8711?: CVE-2026-8711 is a high-severity vulnerability in F5 Nginx Javascript, classified under Heap-based Buffer Overflow. CVSS score: 8.1/10. Published 2026-05-19.
How severe is CVE-2026-8711?: High severity. CVSS v3 base score is 8.1 out of 10.