{"id":"BIT-nginx-2026-42533","summary":"NGINX Map directive and Regex matching vulnerability","details":"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.\n\nImpact:\nThis 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.\n\n\n\n\n Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.","aliases":["BIT-nginx-gateway-2026-42533","CVE-2026-42533"],"modified":"2026-09-08T08:48:16.755577507Z","published":"2026-07-20T20:45:37.138Z","database_specific":{"severity":"Critical","cpes":["cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:*"]},"references":[{"type":"ADVISORY","url":"https://my.f5.com/manage/s/article/K000162097"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42533"}],"affected":[{"package":{"name":"nginx","ecosystem":"Bitnami","purl":"pkg:bitnami/nginx"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.9.6"},{"fixed":"1.30.4"},{"introduced":"1.31.0"},{"fixed":"1.31.3"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/nginx/BIT-nginx-2026-42533.json"},"severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"}]}],"schema_version":"1.9.0"}