Vulnerability · Published May 19, 2026 · Assigned by f5

CVE-2026-8711NGINX JavaScript vulnerability

High 8.1

In plain English

A high-severity heap buffer overflow in NGINX JavaScript from F5. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 9.7% (higher than 96% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.1High

Exploit odds (30 days)9.7%top 4.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Alpine:v3.24	nginx	1.30.2-r1	ALPINE-CVE-2026-8711
Alpine:v3.24	njs	0.9.9-r0	ALPINE-CVE-2026-8711
Debian:14	libnginx-mod-js	0.9.9-1	DEBIAN-CVE-2026-8711
Ubuntu:26.10	libnginx-mod-js	no fix listed	UBUNTU-CVE-2026-8711

Affected products (as reported)

Vendor	Product	Versions
F5	NGINX JavaScript	0.9.4 – before 0.9.9

Weakness: CWE-122 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References

https://my.f5.com/manage/s/article/K000161307 vendor-advisory