Vulnerability · Published Jul 15, 2026 · Assigned by f5
CVE-2026-56434NGINX ngx_http_ssi_module vulnerability
Medium 6.5
In plain English
A medium-severity use-after-free in NGINX Open Source from F5. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.5%top 58.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | nginx | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:9 | nginx | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:9 | nginx | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:10 | nginx-all-modules | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx-all-modules | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx-all-modules | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:9 | nginx-all-modules | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:9 | nginx-all-modules | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:10 | nginx-core | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:9 | nginx-core | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:9 | nginx-core | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:9 | nginx-core | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:10 | nginx-filesystem | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx-filesystem | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx-filesystem | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:9 | nginx-filesystem | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:9 | nginx-filesystem | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:10 | nginx-mod-devel | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx-mod-devel | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx-mod-devel | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:9 | nginx-mod-devel | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:9 | nginx-mod-devel | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:10 | nginx-mod-http-image-filter | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx-mod-http-image-filter | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx-mod-http-image-filter | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:9 | nginx-mod-http-image-filter | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:9 | nginx-mod-http-image-filter | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:10 | nginx-mod-http-perl | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx-mod-http-perl | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx-mod-http-perl | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:9 | nginx-mod-http-perl | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:9 | nginx-mod-http-perl | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:10 | nginx-mod-http-xslt-filter | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx-mod-http-xslt-filter | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx-mod-http-xslt-filter | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:9 | nginx-mod-http-xslt-filter | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:9 | nginx-mod-http-xslt-filter | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:10 | nginx-mod-mail | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx-mod-mail | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx-mod-mail | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| AlmaLinux:9 | nginx-mod-mail | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:9 | nginx-mod-mail | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:10 | nginx-mod-stream | 2:1.26.3-6.el10_2.6 | ALSA-2026:59220 |
| AlmaLinux:8 | nginx-mod-stream | 1:1.24.0-3.module_el8.10.0+4259+e9485ae5.4.alma.1 | ALSA-2026:59216 |
| AlmaLinux:9 | nginx-mod-stream | 1:1.24.0-7.module_el9.8.0+298+469955e3.4.alma.1 | ALSA-2026:59490 |
| AlmaLinux:9 | nginx-mod-stream | 2:1.20.1-28.el9_8.5.alma.1 | ALSA-2026:59362 |
| AlmaLinux:9 | nginx-mod-stream | 2:1.26.3-9.module_el9.8.0+300+0781a894.3 | ALSA-2026:59496 |
| Alpine:v3.21 | nginx | 1.26.3-r2 | ALPINE-CVE-2026-56434 |
| Alpine:v3.22 | nginx | 1.28.3-r6 | ALPINE-CVE-2026-56434 |
| Alpine:v3.23 | nginx | 1.28.3-r6 | ALPINE-CVE-2026-56434 |
| Alpine:v3.24 | nginx | 1.30.4-r0 | ALPINE-CVE-2026-56434 |
| Debian:12 | nginx | 1.22.1-9+deb12u10 | DEBIAN-CVE-2026-56434 |
| Debian:13 | nginx | 1.26.3-3+deb13u8 | DEBIAN-CVE-2026-56434 |
| Debian:14 | nginx | 1.30.1-7 | DEBIAN-CVE-2026-56434 |
| Rocky Linux:10 | nginx | 2:1.26.3-6.el10_2.6 | RLSA-2026:59220 |
| Rocky Linux:8 | nginx | 1:1.24.0-3.module+el8.10.0+40220+e6a4bcb0.2 | RLSA-2026:59216 |
| Rocky Linux:8 | nginx | 1:1.24.0-3.module+el8.10.0+40187+52bedf24.1 | RLSA-2026:59216 |
| Rocky Linux:8 | nginx | 1:1.24.0-3.module+el8.10.0+40249+a5ea815d.3 | RLSA-2026:59216 |
| Rocky Linux:8 | nginx | 1:1.24.0-3.module+el8.10.0+40144+38158758 | RLSA-2026:59216 |
| Rocky Linux:8 | nginx | 1:1.24.0-3.module+el8.10.0+40298+8ed65491.4 | RLSA-2026:59216 |
| Rocky Linux:9 | nginx | 2:1.20.1-28.el9_8.5.rocky.0.1 | RLSA-2026:59362 |
| Rocky Linux:9 | nginx | 1:1.24.0-7.module+el9.8.0+40234+d28db9b8.3.rocky.0.1 | RLSA-2026:59490 |
| Rocky Linux:9 | nginx | 1:1.24.0-7.module+el9.8.0+40218+76099d32.2.rocky.0.1 | RLSA-2026:59490 |
| Rocky Linux:9 | nginx | 1:1.24.0-7.module+el9.8.0+40193+7b2d11e4.1.rocky.0.1 | RLSA-2026:59490 |
| Rocky Linux:9 | nginx | 2:1.26.3-9.module+el9.8.0+40194+40adfc1b | RLSA-2026:59496 |
| Rocky Linux:9 | nginx | 2:1.26.3-9.module+el9.8.0+40222+e48d13b6.1 | RLSA-2026:59496 |
| Rocky Linux:9 | nginx | 2:1.26.3-9.module+el9.8.0+40235+8be1317a.2 | RLSA-2026:59496 |
| Ubuntu:22.04:LTS | nginx | 1.18.0-6ubuntu14.17 | UBUNTU-CVE-2026-56434 |
| Ubuntu:24.04:LTS | nginx | 1.24.0-2ubuntu7.14 | UBUNTU-CVE-2026-56434 |
| Ubuntu:26.04:LTS | nginx | 1.28.3-2ubuntu1.7 | UBUNTU-CVE-2026-56434 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| F5 | NGINX Plus | 37.0.0.1 – before 37.0.3.1R36 – before R36 P7R33 – before * |
| F5 | NGINX Open Source | 1.31.2 – before 1.31.30.8.11 – before 1.30.4 |
Weakness: CWE-416 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
References
- https://my.f5.com/manage/s/article/K000162098 vendor-advisory, patch