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Ubuntu Security Notice USN-7639-2
August 19, 2025

apache2 vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in Apache HTTP Server.

Software Description:
- apache2: Apache HTTP server

Details:

USN-7639-1 fixed several vulnerabilities in Apache. This update
provides the corresponding update for Ubuntu 16.04 LTS, Ubuntu
18.04 LTS, Ubuntu 20.04 LTS, and addressed a regression
fix (LP: #2119395). CVE-2025-49630 and CVE-2025-53020 only
affected Ubuntu 18.04 LTS and Ubuntu 20.04 LTS.

Original advisory details:

 It was discovered that the Apache HTTP Server incorrectly handled
 certain Content-Type response headers. A remote attacker could
 possibly use this issue to perform HTTP response splitting attacks.
 (CVE-2024-42516)

 xiaojunjie discovered that the Apache HTTP Server mod_proxy module
 incorrectly handled certain requests. A remote attacker could
 possibly use this issue to send outbound proxy requests to an
 arbitrary URL. (CVE-2024-43204)

 John Runyon discovered that the Apache HTTP Server mod_ssl module
 incorrectly escaped certain data. A remote attacker could possibly
 use this issue to insert escape characters into log files.
 (CVE-2024-47252)

 Sven Hebrok, Felix Cramer, Tim Storm, Maximilian Radoy, and Juraj
 Somorovsky discovered that the Apache HTTP Server mod_ssl module
 incorrectly handled TLS 1.3 session resumption. A remote attacker
 could possibly use this issue to bypass access control. (CVE-2025-
23048)

 Anthony CORSIEZ discovered that the Apache HTTP Server mod_proxy_http2
 module incorrectly handled missing host headers. A remote attacker
 could possibly use this issue to cause the server to crash, resulting
 in a denial of service. (CVE-2025-49630)

 Robert Merget discovered that the Apache HTTP Server mod_ssl module
 incorrectly handled TLS upgrades. A remote attacker could possibly
 use this issue to hijack an HTTP session. This update removes the
 old "SSLEngine optional" configuration option, possibly requiring
 a configuration change in certain environments. (CVE-2025-49812)

 Gal Bar Nahum discovered that the Apache HTTP Server incorrectly
 handled certain memory operations. A remote attacker could possibly
 use this issue to cause the server to consume resources, leading
 to a denial of service. (CVE-2025-53020)

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+esm2
                                  Available with Ubuntu Pro

Ubuntu 18.04 LTS
  apache2                         2.4.29-1ubuntu4.27+esm6
                                  Available with Ubuntu Pro

Ubuntu 16.04 LTS
  apache2                         2.4.18-2ubuntu3.17+esm16
                                  Available with Ubuntu Pro

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

References:
  https://ubuntu.com/security/notices/USN-7639-2
  https://ubuntu.com/security/notices/USN-7639-1
  CVE-2024-42516, CVE-2024-43204, CVE-2024-47252, CVE-2025-23048,
  CVE-2025-49630, CVE-2025-49812, CVE-2025-53020,
https://launchpad.net/bugs/2119395