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[USN-8563-3] nginx vulnerability

Posted on 19 August 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8563-3
August 19, 2026

nginx vulnerability
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

A security issue was fixed in nginx.

Software Description:
- nginx: small, powerful, scalable web/proxy server

Details:

USN-8563-1 fixed vulnerabilities in nginx. The fix for CVE-2026-42533 was
backed out in USN-8563-2 because it could cause a regression. This update
includes a better fix for CVE-2026-42533.

We apologize for the inconvenience.

Original advisory details:

It was discovered that nginx incorrectly handled certain map directives
using regex matching and capture variables. A remote attacker could use
this issue to cause nginx to crash, resulting in a denial of service, or
possibly execute arbitrary code. (CVE-2026-42533)

It was discovered that nginx had a use-after-free vulnerability in the
ngx_http_ssi_module module when configured with Server-Side Includes,
proxy_pass, and proxy buffering disabled directives. An attacker able to
intercept traffic and control responses from an upstream server could
possibly use this issue to cause nginx to crash, resulting in a denial of
service. (CVE-2026-56434)

It was discovered that nginx incorrectly handled certain requests in the
ngx_http_slice_module module. A remote attacker could possibly use this
issue to obtain sensitive information or cause nginx to crash, resulting
in a denial of service. (CVE-2026-60005)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
nginx 1.28.3-2ubuntu1.9
nginx-core 1.28.3-2ubuntu1.9
nginx-extras 1.28.3-2ubuntu1.9
nginx-full 1.28.3-2ubuntu1.9
nginx-light 1.28.3-2ubuntu1.9

Ubuntu 24.04 LTS
nginx 1.24.0-2ubuntu7.16
nginx-core 1.24.0-2ubuntu7.16
nginx-extras 1.24.0-2ubuntu7.16
nginx-full 1.24.0-2ubuntu7.16
nginx-light 1.24.0-2ubuntu7.16

Ubuntu 22.04 LTS
nginx 1.18.0-6ubuntu14.19
nginx-core 1.18.0-6ubuntu14.19
nginx-extras 1.18.0-6ubuntu14.19
nginx-full 1.18.0-6ubuntu14.19
nginx-light 1.18.0-6ubuntu14.19

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8563-3
https://ubuntu.com/security/notices/USN-8563-2
https://ubuntu.com/security/notices/USN-8563-1
CVE-2026-42533

Package Information:
https://launchpad.net/ubuntu/+source/nginx/1.28.3-2ubuntu1.9
https://launchpad.net/ubuntu/+source/nginx/1.24.0-2ubuntu7.16
https://launchpad.net/ubuntu/+source/nginx/1.18.0-6ubuntu14.19

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