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Ubuntu 26.04 Nginx Severe Denial of Service Regressions USN-8563-2

ubuntu
Calendar Grey July 20, 2026
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Ubuntu USN-8563-2 fixes a regression in Nginx, addressing service disruption risks and reverting problematic updates.
USN-8563-1 introduced a regression in nginx

Summary

USN-8563-1 introduced a regression in nginx

Software Description:

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

Details:

USN-8563-1 fixed vulnerabilities in nginx. One of the fixes introduced ABI

changes that could cause issues with external modules. This update reverts

the fix for CVE-2026-42533 pending further investigation.

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 caus...

Read the Full Advisory

Topics%20covered

Topics Covered

security advisory denial of service critical Ubuntu nginx

Update Instructions

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

Ubuntu 26.04 LTS
  nginx                           1.28.3-2ubuntu1.8
  nginx-core                      1.28.3-2ubuntu1.8
  nginx-extras                    1.28.3-2ubuntu1.8
  nginx-full                      1.28.3-2ubuntu1.8
  nginx-light                     1.28.3-2ubuntu1.8

Ubuntu 24.04 LTS
  nginx                           1.24.0-2ubuntu7.15
  nginx-core                      1.24.0-2ubuntu7.15
  nginx-extras                    1.24.0-2ubuntu7.15
  nginx-full                      1.24.0-2ubuntu7.15
  nginx-light                     1.24.0-2ubuntu7.15

Ubuntu 22.04 LTS
  nginx                           1.18.0-6ubuntu14.18
  nginx-core                      1.18.0-6ubuntu14.18
  nginx-extras                    1.18.0-6ubuntu14.18
  nginx-full                      1.18.0-6ubuntu14.18
  nginx-light                     1.18.0-6ubuntu14.18

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

References

https://ubuntu.com/security/notices/USN-8563-2

https://ubuntu.com/security/notices/USN-8563-1

https://launchpad.net/bugs/2161362

Severity
critical
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Ubuntu Security Notice USN-8563-2

Topics%20covered

Topics Covered

security advisory denial of service critical Ubuntu nginx

Package Information

https://launchpad.net/ubuntu/+source/nginx/1.28.3-2ubuntu1.8
https://launchpad.net/ubuntu/+source/nginx/1.24.0-2ubuntu7.15
https://launchpad.net/ubuntu/+source/nginx/1.18.0-6ubuntu14.18

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