CVE-2026-39828 is a vulnerability in the golang.org/x/crypto/ssh library where an SSH server configured with authentication callbacks returning PartialSuccessError with non-nil permissions discards those permissions silently. This behavior can bypass certificate restrictions like force-command after a second factor authentication succeeds, enabling unauthorized command execution or access. The issue affects Red Hat's Model Transparency CLI image used for signing and verifying AI/ML workloads in the Red Hat Trusted Artifact Signer (RHTAS) product. Red Hat has classified this as an important security flaw with a high severity rating but currently has no available fix or patch. The vulnerability is related to improper preservation of permissions (CWE-281) and impacts confidentiality, integrity, and availability. Red Hat advises monitoring their advisories and working with technical account managers for mitigation guidance.

The vulnerability allows an attacker who can authenticate via SSH with multi-factor authentication to bypass certificate-based restrictions such as force-command, potentially leading to unauthorized command execution or access on affected systems. This impacts confidentiality, integrity, and availability of the affected Red Hat systems using the vulnerable golang.org/x/crypto/ssh library. The flaw undermines the intended security controls in place for SSH certificate restrictions.

Red Hat currently does not provide an official fix or patch for this vulnerability. Available mitigation options do not meet Red Hat's criteria for ease of use, deployment, or applicability. Users are advised to monitor Red Hat advisories for updates and consult with Red Hat Technical Account Managers if available. No direct workaround is provided by Red Hat at this time.