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Ubuntu Apache2 Important DoS HTTP Response Issues USN-8571-1

ubuntu
Calendar Grey July 20, 2026
Scroller Ubuntu
Critical updates for Apache HTTP Server vulnerabilities across Ubuntu versions enhance security in your environment.
Several security issues were fixed in Apache HTTP Server.

Summary

Several security issues were fixed in Apache HTTP Server.

Software Description:

- apache2: Apache HTTP server

Details:

Pavel Kohout and Arkadi Vainbrand discovered that Apache HTTP Server

incorrectly handled certain memory operations in mod_authn_socache. A

remote attacker could possibly use this issue to cause a denial of service.

(CVE-2026-33007)

Haruki Oyama, Merih Mengisteab, and Dawit Jeong discovered that Apache

HTTP Server had an HTTP response splitting vulnerability in multiple

modules when used with untrusted or compromised backend servers. An

attacker could possibly use this issue to inject arbitrary HTTP headers.

(CVE-2026-33523)

Elhanan Haenel discovered that Apache HTTP Server incorrectly handled

certain memory operations in mod_proxy_ajp. A remote attacker could

possibly use this issue to cause a denial of service. (CVE-2026-33857)

Tianshuo Han and Jérôme Djouder discovered that Apache HTTP Server

incorrectly handled certain string operations in mod_proxy_ajp....

Read the Full Advisory

Topics%20covered

Topics Covered

security advisory denial of service Ubuntu important apache2 http response splitting

Update Instructions

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

Ubuntu 20.04 LTS
  apache2                         2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro
  apache2-bin                     2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro
  apache2-dev                     2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro
  apache2-ssl-dev                 2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro
  apache2-suexec-custom           2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro
  apache2-suexec-pristine         2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro
  apache2-utils                   2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro
  libapache2-mod-md               2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro
  libapache2-mod-proxy-uwsgi      2.4.41-4ubuntu3.23+esm5
                                  Available with Ubuntu Pro

Ubuntu 18.04 LTS
  apache2                         2.4.29-1ubuntu4.27+esm10
                                  Available with Ubuntu Pro
  apache2-bin                     2.4.29-1ubuntu4.27+esm10
                                  Available with Ubuntu Pro
  apache2-dev                     2.4.29-1ubuntu4.27+esm10
                                  Available with Ubuntu Pro
  apache2-ssl-dev                 2.4.29-1ubuntu4.27+esm10
                                  Available with Ubuntu Pro
  apache2-suexec-custom           2.4.29-1ubuntu4.27+esm10
                                  Available with Ubuntu Pro
  apache2-suexec-pristine         2.4.29-1ubuntu4.27+esm10
                                  Available with Ubuntu Pro
  apache2-utils                   2.4.29-1ubuntu4.27+esm10
                                  Available with Ubuntu Pro

Ubuntu 16.04 LTS
  apache2                         2.4.18-2ubuntu3.17+esm19
                                  Available with Ubuntu Pro
  apache2-bin                     2.4.18-2ubuntu3.17+esm19
                                  Available with Ubuntu Pro
  apache2-dev                     2.4.18-2ubuntu3.17+esm19
                                  Available with Ubuntu Pro
  apache2-suexec-custom           2.4.18-2ubuntu3.17+esm19
                                  Available with Ubuntu Pro
  apache2-suexec-pristine         2.4.18-2ubuntu3.17+esm19
                                  Available with Ubuntu Pro
  apache2-utils                   2.4.18-2ubuntu3.17+esm19
                                  Available with Ubuntu Pro

Ubuntu 14.04 LTS
  apache2                         2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-bin                     2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-dev                     2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-mpm-event               2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-mpm-itk                 2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-mpm-prefork             2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-mpm-worker              2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-suexec                  2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-suexec-custom           2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-suexec-pristine         2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2-utils                   2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  apache2.2-bin                   2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  libapache2-mod-macro            1:2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro
  libapache2-mod-proxy-html       1:2.4.7-1ubuntu4.22+esm14
                                  Available with Ubuntu Pro

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

References

https://ubuntu.com/security/notices/USN-8571-1

CVE-2026-33007, CVE-2026-33523, CVE-2026-33857, CVE-2026-34032,

CVE-2026-34355, CVE-2026-34356, CVE-2026-42535, CVE-2026-42536,

CVE-2026-43951, CVE-2026-44119, CVE-2026-44185, CVE-2026-44186,

CVE-2026-44631, CVE-2026-48913, CVE-2026-49975

Severity
important
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-8571-1

Topics%20covered

Topics Covered

security advisory denial of service Ubuntu important apache2 http response splitting

Package Information

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