CVE-2026-56624 in MINA SSHD
Summary
by MITRE • 07/21/2026
Improper certificate validation in Apache MINA SSHD (server-side). Apache MINA SSHD is a Java library for client-side and server-side SSH.
Server-side OpenSSH user certificate validation during user authentication in an Apache MINA SSHD server did not check for the unsupported force-command or verify-required options that could be embedded in the certificate, nor did it validate these options. As a result it was possible that a user could authenticate with such a certificate that included a force-command option but still was able to execute other commands. What other command exactly would be available to the user depends on the implementation of the server.
This issue is fixed in Apache MINA SSHD 2.19.0 and 3.0.0-M5. Applications are advised to upgrade to these versions.
The fix rejects OpenSSH user certificates that include these options, since Apache MINA SSHD implements neither force-command nor sk-*[email protected] user certificates (which are the only ones for which verify-required would make sense).
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Analysis
by VulDB Data Team • 07/21/2026
The vulnerability in Apache MINA SSHD represents a critical security flaw in server-side certificate validation mechanisms that directly impacts the integrity of SSH authentication processes. This issue specifically affects the validation of OpenSSH user certificates within the MINA SSHD library, which serves as a Java-based implementation for both client and server SSH functionality. The flaw stems from inadequate verification of certificate attributes that are essential for maintaining proper access controls and command execution restrictions.
The technical root cause lies in the failure to properly validate force-command and verify-required options embedded within OpenSSH user certificates during the authentication process. These options are designed to restrict command execution to specific commands or verify certain conditions before allowing authentication to proceed. When such certificates are processed without proper validation, they can be exploited to bypass intended restrictions, allowing authenticated users to execute commands beyond their designated permissions. This represents a classic privilege escalation vulnerability that undermines the principle of least privilege in security implementations.
The operational impact of this vulnerability extends beyond simple authentication bypasses and creates significant risks for server security posture. Attackers who can craft malicious certificates with force-command options could potentially gain unauthorized access to additional system resources or execute arbitrary commands that should be restricted based on certificate policies. The exact scope of available commands depends on the specific server implementation, but the fundamental risk remains consistent across deployments where proper certificate validation is not enforced. This vulnerability affects organizations relying on MINA SSHD for secure remote access management and could lead to data breaches or system compromise if exploited.
From a cybersecurity framework perspective, this issue maps directly to CWE-295 Certificate Validation Errors, which encompasses failures in validating certificate attributes and their associated constraints. The vulnerability also aligns with ATT&CK technique T1566.003 Credential Stuffing and T1078 Valid Accounts, as it enables attackers to leverage valid certificates while bypassing intended access controls. The fix implemented in Apache MINA SSHD versions 2.19.0 and 3.0.0-M5 addresses this by rejecting OpenSSH user certificates containing these problematic options, effectively preventing the exploitation vector while maintaining compatibility with legitimate certificate usage patterns.
Organizations using affected versions of Apache MINA SSHD must prioritize immediate upgrade to mitigate this vulnerability, as continued operation with vulnerable software exposes systems to potential unauthorized command execution. The recommended mitigation strategy focuses on implementing the patched versions that explicitly reject certificates containing force-command and verify-required options, ensuring that only properly validated certificates are accepted for authentication. This approach aligns with security best practices for certificate-based authentication and helps maintain the integrity of SSH access controls across enterprise environments relying on MINA SSHD implementations.