CVE-2025-61985 is a security vulnerability identified in OpenSSH versions prior to 10.1, related to improper neutralization of the null byte ('\0') character within ssh:// URIs. The vulnerability is categorized under CWE-158, which concerns improper neutralization of null bytes that can lead to unexpected behavior in string processing. In this case, the ssh client fails to correctly handle the null byte embedded in the URI, which can be exploited when a ProxyCommand is configured. ProxyCommand allows SSH clients to specify an external command to connect to the SSH server, often used for proxying or tunneling connections. The presence of a null byte in the URI can truncate or manipulate the command string, potentially enabling an attacker to execute arbitrary code or commands on the client machine. The CVSS 3.1 base score is 3.6, reflecting low severity due to the requirement for local access (AV:L), high attack complexity (AC:H), and the need for low privileges (PR:L) but no user interaction (UI:N). The impact affects confidentiality and integrity to a limited extent, with no availability impact. No public exploits have been reported yet, and no patches are linked in the provided data, but upgrading to OpenSSH 10.1 or later is recommended to remediate the issue.

For European organizations, the impact of CVE-2025-61985 is relatively low but non-negligible. The vulnerability could allow an attacker with local access and low privileges to execute arbitrary code on systems where OpenSSH clients prior to version 10.1 are used with ProxyCommand configurations. This could lead to unauthorized disclosure or modification of sensitive information, especially in environments where SSH is heavily used for secure communications and automation. Organizations in sectors such as finance, government, and critical infrastructure that rely on OpenSSH for secure remote access and proxying may face increased risk if this vulnerability is exploited. However, the high attack complexity and requirement for local access reduce the likelihood of widespread exploitation. Nonetheless, the presence of this vulnerability could be leveraged as part of a multi-stage attack chain, increasing overall risk posture.

To mitigate CVE-2025-61985, European organizations should: 1) Upgrade all OpenSSH clients to version 10.1 or later where the vulnerability is fixed. 2) Audit and review all ProxyCommand configurations to ensure they do not process untrusted input or ssh:// URIs containing null bytes. 3) Implement strict input validation and sanitization for any scripts or commands invoked via ProxyCommand. 4) Restrict local user privileges to minimize the risk of exploitation by low-privilege users. 5) Monitor logs for unusual ProxyCommand usage or SSH client errors that may indicate attempted exploitation. 6) Educate system administrators and users about the risks of using outdated OpenSSH versions and unsafe ProxyCommand practices. 7) Employ host-based intrusion detection systems to detect anomalous command executions related to SSH client activity. These steps go beyond generic advice by focusing on the specific vector (ProxyCommand and ssh:// URI handling) and the operational context of the vulnerability.