When NGINX Plus is configured to use the Message Queuing Telemetry Transport (MQTT) filter module (ngxstreammqttfiltermodule), unauthenticated attackers can send requests with conditions beyond the attacker's control to cause a heap buffer over-read in the NGINX worker process, leading to a restart.

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.

Last updated 20 July 2026

Last updated 20 July 2026