What is CVE-2026-56434?

CVE-2026-56434 is a medium-severity vulnerability in F5 Nginx Open Source, classified under Use After Free. CVSS score: 6.5/10. Published 2026-07-15.

How severe is CVE-2026-56434?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Use After Free in F5 Nginx Open Source

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 configurati…

Vulnerability class: Use-After-Free

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H.

Affected products

F5 Nginx Open Source — versions 1.31.2, 0.8.11
F5 Nginx Plus — versions 37.0.0.1, R36, R33

Weakness classification (CWE)

CWE-416 — Use After Free

References

f5sirt@f5.com (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-56434?: CVE-2026-56434 is a medium-severity vulnerability in F5 Nginx Open Source, classified under Use After Free. CVSS score: 6.5/10. Published 2026-07-15.
How severe is CVE-2026-56434?: Medium severity. CVSS v3 base score is 6.5 out of 10.