SB2023122834 - Debian update for libssh
Published: December 28, 2023 Updated: January 31, 2025
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 3 secuirty vulnerabilities.
1) OS Command Injection (CVE-ID: CVE-2023-6004)
The vulnerability allows a remote attacker to execute arbitrary shell commands on the target system.
The vulnerability exists due to improper input validation in OpenSSH client. If an invalid user or hostname that contained shell metacharacters was passed to ssh(1), and a ProxyCommand, LocalCommand directive or "match exec" predicate referenced the user or hostname via %u, %h or similar expansion token, then an attacker who could supply arbitrary user/hostnames to ssh(1) could potentially perform command injection depending on what quoting was present in the user-supplied ssh_config(5) directive.
2) Unchecked Return Value (CVE-ID: CVE-2023-6918)
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to libssh does not check for returned values of message digest (MD) operations in low memory conditions. A remote attacker can terminate the connection or force the library to use weak keys.
3) Inadequate encryption strength (CVE-ID: CVE-2023-48795)
The vulnerability allows a remote attacker to perform MitM attack.
The vulnerability exists due to incorrect implementation of the SSH Binary Packet Protocol (BPP), which mishandles the handshake phase and the use of sequence numbers. A remote attacker can perform MitM attack and delete the SSH2_MSG_EXT_INFO message sent before authentication starts, allowing the attacker to disable a subset of the keystroke timing obfuscation features introduced in OpenSSH 9.5.
The vulnerability was dubbed "Terrapin attack" and it affects both client and server implementations.
Remediation
Install update from vendor's website.