CVE-2026-42533: F5 Nginx Gateway Fabric

High severity, CVSS 8.1. EPSS: 0.9% chance of exploitation in the next 30 days.

A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control 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. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. There is no control plane exposure; this is a data plane issue only.  Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Affected products

• F5 Nginx Gateway Fabric: from 1.3.0, up to and including 1.6.2; from 2.0.0, before 2.6.7 (fixed in 2.6.7)
• F5 Nginx Ingress Controller: from 3.5.0, up to and including 3.7.2; from 5.0.0, before 5.5.3 (fixed in 5.5.3); from 2026-lts-r1, before 2026-lts-r4 (fixed in 2026-lts-r4); version 4.0.0 only; version 4.0.1 only
• F5 Nginx Plus: from 37.0.0.1, before 37.0.3.1 (fixed in 37.0.3.1); from r33, before r36 (fixed in r36); version r36 only
• F5 Waf: from 4.11.0, up to and including 4.16.0; from 5.2.0, up to and including 5.8.0; from 5.9.0, before 5.13.4 (fixed in 5.13.4)

Published 2026-07-15. Last modified 2026-08-10.