CVE-2026-93479: NGINX map directive and regex matching vulnerability
A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and the root directive or access log format 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 Software
Event History
Frequently Asked Questions
Which deployments are exposed?
NGINX Plus and NGINX Open Source deployments are affected when a map directive uses regex matching and the root directive or access-log format references the map regex capture variables before the map output variable. The issue can also occur when a non-cacheable variable is used in a string expression under certain conditions.
Does exploitation require authentication or control-plane access?
No authentication or control-plane access is required. This is a data-plane issue that can be triggered through crafted HTTP requests, although exploitation also depends on conditions beyond the attacker's control.
What is the likely impact if exploitation succeeds?
The overflow can cause the NGINX worker process to restart, resulting in denial of service. Code execution may also be possible where ASLR is disabled or the attacker can bypass ASLR.