CVE-2026-42530

A flaw was found in the ngx_http_v3_module module of NGINX. When NGINX is configured to use the HTTP/3 QUIC module, an attacker can use a specially crafted HTTP/3 session to reopen a QPACK encoder stream and cause a use-after-free issue, potentially allowing code execution or a denial of service by forcing the process to restart.

This vulnerability is only exploitable when NGINX is configured to use the HTTP/3 QUIC module. This issue allows a remote unauthenticated attacker to potentially execute arbitrary code or cause a denial of service by forcing the worker process to restart.

Default Red Hat Enterprise Linux security features, including SELinux enforcement, Address Space Layout Randomization (ASLR) and NX (No-Execute) stack protection, significantly increase the difficulty of achieving arbitrary code execution, limiting the impact of this vulnerability.

Due to these reasons, this vulnerability has been rated with an important severity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this vulnerability, disable HTTP/3 by removing quic from all listen directives.