CVE-2026-8711: F5 Njs

Critical severity, CVSS 9.8. EPSS: 0.8% chance of exploitation in the next 30 days.

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 products

• F5 Njs: from 0.9.4, before 0.9.9 (fixed in 0.9.9)

Published 2026-05-19. Last modified 2026-07-23.