CVE-2026-56434

MEDIUM 6.5

NGINX ngx_http_ssi_module vulnerability

CVSS Score

6.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-416
Vendor	f5
Product	nginx plus
Published	Jul 15, 2026
Last Updated	Jul 15, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

High

Affected Versions

F5 / NGINX Plus

37.0.0.1 < 37.0.3.1 R36 < R36 P7 R33 < *

F5 / NGINX Open Source

1.31.2 < 1.31.3 0.8.11 < 1.30.4

References

NVD ↗ CVE.org ↗ EPSS Data ↗

my.f5.com: https://my.f5.com/manage/s/article/K000162098

Credits

🔍 F5 acknowledges p4p3r(@P4P3R-HAK)" of "싸이버원(CYBERONE) for bringing this issue to our attention and following the highest standards of coordinated disclosure.