CVE-2026-56434
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.
How to fix
- f5 nginx_gateway_fabric2.6.7 or later
- f5 nginx_ingress_controller5.5.3, 2026-lts-r4 or later
- f5 nginx_plus37.0.3.1, r36 or later
- f5 waf5.13.4 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| f5 nginx_gateway_fabric | 1.3.0 ≤ v ≤ 1.6.2, 2.0.0 ≤ v < 2.6.7 | 2.6.7 |
| f5 nginx_ingress_controller | 3.5.0 ≤ v ≤ 3.7.2, 5.0.0 ≤ v < 5.5.3, 2026-lts-r1 ≤ v < 2026-lts-r4, 4.0.0, 4.0.1 | 5.5.3, 2026-lts-r4 |
| f5 nginx_plus | 37.0.0.1 ≤ v < 37.0.3.1, r33 ≤ v < r36, r36 | 37.0.3.1, r36 |
| f5 waf | 4.11.0 ≤ v ≤ 4.16.0, 5.2.0 ≤ v ≤ 5.8.0, 5.9.0 ≤ v < 5.13.4 | 5.13.4 |
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