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.

Score

CVSS 4.0 8.3 High

Status

Analyzed - f5sirt@f5.com

Published

2026-07-15

Last modified

2026-07-15

Weaknesses

CWE-416

Affected products

• Nginx Gateway Fabric (F5)
• Nginx Ingress Controller (F5)
• Nginx Open Source (F5)
• Nginx Plus (F5)
• Waf (F5)

References

• https://my.f5.com/manage/s/article/K000162098