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)…

PriorityP342medium6.5CVSS 3.1

AVNACHPRNUINSUCNILAH

EPSS

0.39%

31.0th percentile

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.

Affected

6 ranges

Vendor	Product	Version range	Fixed in
f5	nginx_open_source	>= 0.8.11 < 1.30.4	1.30.4
f5	nginx_open_source	>= 1.31.2 < 1.31.3	1.31.3
f5	nginx_plus	—	—
f5	nginx_plus	>= 37.0.0.1 < 37.0.3.1	37.0.3.1
f5	nginx_plus	>= R33 < *	*
f5	nginx_plus	>= R36 < R36 P7	R36 P7

CVSS provenance

nvdv3.16.5MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

nvdv4.08.3HIGHCVSS: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

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