Vulnerability Description
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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| F5 | Nginx Gateway Fabric | >= 1.3.0, <= 1.6.2 |
| F5 | Nginx Ingress Controller | >= 3.5.0, <= 3.7.2 |
| F5 | Nginx Plus | >= 37.0.0.1, < 37.0.3.1 |
| F5 | Waf | >= 4.11.0, <= 4.16.0 |
Related Weaknesses (CWE)
References
- https://my.f5.com/manage/s/article/K000162098Vendor Advisory
FAQ
What is CVE-2026-56434?
CVE-2026-56434 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 directive...
How severe is CVE-2026-56434?
CVE-2026-56434 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-56434?
Check the references section above for vendor advisories and patch information. Affected products include: F5 Nginx Gateway Fabric, F5 Nginx Ingress Controller, F5 Nginx Plus, F5 Waf.