CVE-2025-32728: OpenBSD OpenSSH Forwarding Vulnerability

CVE-2025-32728 Overview

In sshd in OpenSSH before 10.0, the DisableForwarding directive does not adhere to the documentation stating that it disables X11 and agent forwarding.

Critical Impact
Although the vulnerability is categorized as low severity, it can lead to unexpected behavior in environments relying on disabling X11 and agent forwarding.

Affected Products

OpenBSD OpenSSH
Debian Debian Linux

Discovery Timeline

Not Available - Vulnerability discovered by Not Available
Not Available - Responsible disclosure to openbsd
Not Available - CVE CVE-2025-32728 assigned
Not Available - openbsd releases security patch
2025-04-10 - CVE CVE-2025-32728 published to NVD
2025-05-22 - Last updated in NVD database

Technical Details for CVE-2025-32728

Vulnerability Analysis

The vulnerability involves a misbehavior of the DisableForwarding directive, which does not prevent X11 and agent forwarding as intended. This discrepancy could lead to unintended information flows, posing security risks in sensitive environments.

Root Cause

The root cause is attributed to improper handling and enforcement in the code related to the DisableForwarding settings.

Attack Vector

Local

yaml

# This reflects a configuration example
Host *
    DisableForwarding yes

Detection Methods for CVE-2025-32728

Indicators of Compromise

Unusual SSH authentication successes with forwarding enabled
Logs showing unexpected forwarding usage
Anomalous network traffic indicative of X11 or agent forwarding

Detection Strategies

Inspect SSH configurations and monitor logs for unauthorized forwarding attempts, particularly where DisableForwarding should enforce stricter controls.

Monitoring Recommendations

Utilize network intrusion detection systems (NIDS) to alert on unusual forwarding patterns. Regularly audit SSH logs for unexpected activity with a focus on Forwarding parameters.

How to Mitigate CVE-2025-32728

Immediate Actions Required

Review SSH configurations across all systems
Deploy the latest OpenSSH patches
Audit network traffic and authentication logs

Patch Information

Patches are available and can be found at the OpenSSH GitHub repository.

Workarounds

Ensure SSH configurations explicitly set forwarding options in accordance with documentation and organizational policies. Consider additional measures such as network-level restrictions on forwarding channels if an environment requires it.

bash

# Consider modifying SSHD configuration with stricter settings
sudo vi /etc/ssh/sshd_config

# Enforce the desired security posture
PermitX11Forwarding no
AllowAgentForwarding no