Pierluigi Paganini October 16, 2026

F5 addressed multiple vulnerabilities, including critical RCE flaws in NGINX that attackers could exploit without authentication.

Security and application delivery firm F5 announced fixes for eleven security issues in NGINX. Among them, critical vulnerabilities tracked as CVE-2026-15176 and CVE-2026-93479 could be exploited without authentication via crafted HTTP requests.

Under certain conditions beyond their control, an unauthenticated attacker could exploit the security flaws to trigger a buffer overflow leading to a restart. If ASLR is disabled or can be bypassed, the attacker could achieve RCE.

The flaw CVE-2026-15176 (CVSS score of 9.2) is a heap-based buffer overflow vulnerability in NGINX Plus and NGINX Open Source that could allow an unauthenticated attacker to trigger a denial-of-service condition or potentially execute arbitrary code by sending crafted HTTP requests. The vulnerability occurs under specific configurations involving the alias directive and the $request_filename variable. Remote code execution may be possible if ASLR is disabled or bypassed.

The flaw CVE-2026-93479 (CVSS score of 9.2) is a heap-based buffer overflow vulnerability in NGINX Plus and NGINX Open Source that could allow an unauthenticated attacker to trigger a denial-of-service condition or potentially execute arbitrary code through crafted HTTP requests. It affects specific configurations where regular-expression capture variables from the map directive are referenced before the map output variable, or where a non-cacheable variable is used in a string expression under certain conditions. Remote code execution may be possible if ASLR is disabled or bypassed.

The third critical flaw fixed by the vendor, tracked as CVE-2026-97205 (CVSS score of 9.2), is a use-after-free vulnerability in NGINX ngx_http_core_module that, under certain configurations with asynchronous file I/O (AIO) enabled, may cause memory corruption or unexpected worker process termination when processing Server Side Includes (SSI) pages containing include virtual commands. A remote attacker could exploit the flaw to cause a denial-of-service (DoS) or potentially execute code, particularly when ASLR is disabled or can be bypassed.

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Pierluigi Paganini

(SecurityAffairs – hacking, NGINX)