CVE-2026-42533

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.

• f5 nginx gateway fabric (>= 1.3.0 <= 1.6.2) • f5 nginx gateway fabric (>= 2.0.0 < 2.6.7) • f5 nginx ingress controller (>= 3.5.0 <= 3.7.2) • f5 nginx ingress controller (>= 5.0.0 < 5.5.3) • f5 nginx ingress controller (>= 2026-lts-r1 < 2026-lts-r4) • f5 nginx ingress controller 4.0.0 • f5 nginx ingress controller 4.0.1 • f5 nginx plus (>= 37.0.0.1 < 37.0.3.1) • f5 nginx plus (>= r33 < r36) • f5 nginx plus r36 • f5 waf (>= 4.11.0 <= 4.16.0) • f5 waf (>= 5.2.0 <= 5.8.0) • f5 waf (>= 5.9.0 < 5.13.4)