SB2025091577 - Ubuntu update for libssh

Description

This security bulletin contains information about 7 secuirty vulnerabilities.

1) Integer overflow (CVE-ID: CVE-2025-4877)

The vulnerability allows a local user to execute arbitrary code on the target system.

The vulnerability exists due to integer overflow within the bin_to_base64() function in base64.c. A local user can trigger an integer overflow and execute arbitrary code on the target system.

Note, the vulnerability can be exploited only via the ssh_get_fingerprint_hash() function on 32-bit builds in case the API is (mis)used and a libssh consumer passes in an unexpectedly large input buffer.

2) Use-after-free (CVE-ID: CVE-2025-4878)

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a use-after-free error within the privatekey_from_file() function. A local user can trigger a use-after-free error and execute arbitrary code with elevated privileges. 

3) Out-of-bounds read (CVE-ID: CVE-2025-5318)

The vulnerability allows a remote user to gain access to potentially sensitive information.

The vulnerability exists due to a boundary condition within the sftp_handle() function. A remote user can trigger an out-of-bounds read error and read contents of memory on the system.

4) Integer overflow (CVE-ID: CVE-2025-5449)

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to an incorrect packet length check within the SFTP server message decoding logic when handling large payload sizes on 32-bit systems. A remote attacker can trick the victim into connecting to a malicious server, trigger an integer overflow and crash the application.

5) Double free (CVE-ID: CVE-2025-5351)

The vulnerability allows a remote user to perform a denial of service (DoS) attack.

The vulnerability exists due to a boundary error in the internal function responsible for converting cryptographic keys into serialized formats. A remote user can trigger a double free error and perform a denial of service attack in low-memory scenarios.

6) Incorrect calculation (CVE-ID: CVE-2025-5372)

The vulnerability allows a remote user to perform MitM attack.

The vulnerability exist due to incorrect calculation within the ssh_kdf() function responsible for key derivation when built with OpenSSL versions older than 3.0. A remote user can compromise the integrity of the SSH session. 

7) Return of Wrong Status Code (CVE-ID: CVE-2025-5987)

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to incorrect handling of the wrong status code returned by the OpenSSL within the chacha20_poly1305_set_key() function when using the ChaCha20 cipher with the OpenSSL library. A remote attacker can force the library to partially initialize cipher context, leading to an undefined application's behavior.

Remediation

Install update from vendor's website.

References

• https://ubuntu.com/security/notices/USN-7619-1