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Ubuntu Security Notice USN-7696-1
August 14, 2025

libssh 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 libssh.

Software Description:
- libssh: A tiny C SSH library

Details:

Ronald Crane discovered that libssh incorrectly handled certain base64
conversions. An attacker could use this issue to cause libssh to crash,
resulting in a denial of service, or possibly execute arbitrary code.
(CVE-2025-4877)

Ronald Crane discovered that libssh incorrectly handled the
privatekey_from_file() function. An attacker could use this issue to cause
libssh to crash, resulting in a denial of service, or possibly execute
arbitrary code. (CVE-2025-4878)

Ronald Crane discovered that libssh incorrectly handled certain memory
operations in the sftp server. An attacker could possibly use this issue
to cause libssh to crash, resulting in a denial of service.
(CVE-2025-5318)

Update instructions:

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

Ubuntu 20.04 LTS
  libssh-4                        0.9.3-2ubuntu2.5+esm1
                                  Available with Ubuntu Pro

Ubuntu 18.04 LTS
  libssh-4                        0.8.0~20170825.94fa1e38-1ubuntu0.7+esm4
                                  Available with Ubuntu Pro

Ubuntu 16.04 LTS
  libssh-4                        0.6.3-4.3ubuntu0.6+esm2
                                  Available with Ubuntu Pro

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

References:
  https://ubuntu.com/security/notices/USN-7696-1
  CVE-2025-4877, CVE-2025-4878, CVE-2025-5318