A newly disclosed security flaw, CVE-2026-42533, has revealed a critical Pre-Auth nginx vulnerability that could allow attackers to achieve reliable RCE (remote code execution) without authentication. The issue affects nginx versions 0.9.6 through 1.30.3 (stable) and 1.31.2 (mainline), while patched releases include 1.30.4 and 1.31.3. Affected NGINX Plus versions include R33-R36 (fixed in R36 P7) and 37.0.0.1-37.0.2.1 (fixed in 37.0.3.1). 

According to the disclosure, the vulnerability stems from a missing save-and-restore mechanism for PCRE capture state within nginx's two-pass script evaluation engine. The flaw enables attackers to trigger a heap buffer overflow with attacker-controlled...