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Ubuntu Security Notice USN-6592-2
February 05, 2024

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

- Ubuntu 18.04 LTS (Available with Ubuntu Pro)
- Ubuntu 16.04 LTS (Available with Ubuntu Pro)

Summary:

Several security issues were fixed in libssh.

Software Description:
- libssh: A tiny C SSH library

Details:

USN-6592-1 fixed vulnerabilities in libssh. This update provides the
corresponding updates for Ubuntu 16.04 LTS and Ubuntu 18.04 LTS.

Original advisory details:

It was discovered that libssh incorrectly handled the ProxyCommand and the
ProxyJump features. A remote attacker could possibly use this issue to
inject malicious code into the command of the features mentioned through
the hostname parameter. (CVE-2023-6004)

It was discovered that libssh incorrectly handled return codes when
performing message digest operations. A remote attacker could possibly use
this issue to cause libssh to crash, obtain sensitive information, or
execute arbitrary code. (CVE-2023-6918)

Update instructions:

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

Ubuntu 18.04 LTS (Available with Ubuntu Pro):
libssh-4 0.8.0~20170825.94fa1e38-1ubuntu0.7+esm3
libssh-gcrypt-4 0.8.0~20170825.94fa1e38-1ubuntu0.7+esm3

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
libssh-4 0.6.3-4.3ubuntu0.6+esm1
libssh-gcrypt-4 0.6.3-4.3ubuntu0.6+esm1

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

References:
https://ubuntu.com/security/notices/USN-6592-2
https://ubuntu.com/security/notices/USN-6592-1
CVE-2023-6004, CVE-2023-6918