CVE-2026-56434
NGINX ngx_http_ssi_module 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.
How to fix CVE-2026-56434
To remediate CVE-2026-56434, upgrade the affected package to a fixed version below.
- —upgrade to 1.26.3-r2 or later
- —upgrade to 1.30.4 or later
- —upgrade to 1.30.4 or later
- —no fix listed
Is CVE-2026-56434 being exploited?
Low — EPSS is 0.4%, meaning exploitation activity has not been observed at scale.
Affected packages (4)
- from 0, < 1.26.3-r2
- >= 0.8.11, < 1.30.4, >= 1.31.2, < 1.31.3
- >= 0.8.11, < 1.30.4, >= 1.31.2, < 1.31.3
- from 0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |