CVE-2026-56434

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssi_module module. This vulnerability may exist when the Server-Side Includes (SSI), proxy_pass, and proxy_buffering off directives are configured. With this configuration, an unauthenticated attacker with man-in-the-middle (MITM) ability to control responses from an upstream server may be able to cause a use-after-free in the NGINX worker process. This issue may lead to limited modification of memory or a restart of the NGINX worker process. Impact: This vulnerability may allow remote attackers to have limited control to modify memory contents or restart the NGINX worker process. 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.

• f5 nginx gateway fabric (>= 1.3.0 <= 1.6.2) • f5 nginx gateway fabric (>= 2.0.0 < 2.6.7) • f5 nginx ingress controller (>= 3.5.0 <= 3.7.2) • f5 nginx ingress controller (>= 5.0.0 < 5.5.3) • f5 nginx ingress controller (>= 2026-lts-r1 < 2026-lts-r4) • f5 nginx ingress controller 4.0.0 • f5 nginx ingress controller 4.0.1 • f5 nginx plus (>= 37.0.0.1 < 37.0.3.1) • f5 nginx plus (>= r33 < r36) • f5 nginx plus r36 • f5 waf (>= 4.11.0 <= 4.16.0) • f5 waf (>= 5.2.0 <= 5.8.0) • f5 waf (>= 5.9.0 < 5.13.4)