CVE intelligence

CVE-2026-56434

Vulnerability intelligence

Published Jul 15, 2026Sources checked Oct 28, 2026

6.5MEDIUMCVSS out of 10

What this means

Review the available evidence

CVE-2026-56434 and is rated Medium severity with a CVSS score of 6.5. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Ubuntu Security Notices guidance

Vendor revision: Sep 14, 2026

USN-8563-1 fixed vulnerabilities in nginx.

Ubuntu Security Notices guidance

Vendor revision: Aug 19, 2026

USN-8563-3 fixed a vulnerability in nginx.

Ubuntu Security Notices guidance

Vendor revision: Aug 19, 2026

USN-8563-1 fixed vulnerabilities in nginx.

CISA KEVNot listedBased on the latest collected catalog

EPSS0.4%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is 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), 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.

Source: NVD