CVE-2025-59339 in the-bastion
Summary
by MITRE • 09/17/2025
The Bastion provides authentication, authorization, traceability and auditability for SSH accesses. Session-recording ttyrec files, may be handled by the provided osh-encrypt-rsync script that is a helper to rotate, encrypt, sign, copy, and optionally move them to a remote storage periodically, if configured to. When running, the script properly rotates and encrypts the files using the provided GPG key(s), but silently fails to sign them, even if asked to.
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Analysis
by VulDB Data Team • 09/18/2025
The vulnerability identified as CVE-2025-59339 affects the Bastion system's session recording functionality, specifically within the osh-encrypt-rsync script that manages the lifecycle of ttyrec files. This script serves as a critical component in the security infrastructure by handling the rotation, encryption, signing, and remote storage of SSH session recordings. The Bastion system is designed to provide comprehensive authentication, authorization, traceability, and auditability for SSH accesses, making the integrity and authenticity of session recordings paramount to maintaining security posture. The vulnerability manifests when the script executes its intended functions but fails to perform digital signature operations on the encrypted ttyrec files, despite being configured to do so. This represents a significant deviation from expected security behavior where cryptographic signatures are essential for ensuring file integrity and authenticity.
The technical flaw resides in the osh-encrypt-rsync script's implementation where it properly handles encryption using GPG keys but silently omits the signing step even when explicitly configured to perform this operation. This silent failure represents a critical security gap that violates the principle of least privilege and fails to maintain the integrity of audit trails. The vulnerability can be categorized under CWE-311 as "Missing Encryption of Sensitive Data" and CWE-312 as "Sensitive Data in Transient Storage" since the encrypted files lack proper digital signatures that would verify their authenticity and integrity. The script's behavior demonstrates a failure in proper error handling and validation, where the absence of signing operations occurs without any notification or logging of the failure, making it invisible to administrators and security monitoring systems.
The operational impact of this vulnerability is severe as it undermines the entire audit and compliance framework that the Bastion system is designed to support. When session recordings are encrypted but not signed, security teams cannot verify that the files have not been tampered with since the digital signatures that would confirm authenticity are missing. This creates a false sense of security where administrators believe their session recordings are properly secured and authenticated, when in reality they are vulnerable to manipulation without detection. The vulnerability directly impacts the system's ability to meet regulatory compliance requirements such as those outlined in NIST SP 800-53 and ISO 27001, which mandate proper cryptographic controls for audit data. Attackers could potentially replace legitimate session recordings with malicious content, and the lack of signatures would make it impossible to detect such tampering, creating a significant risk for forensic investigations and compliance audits.
Mitigation strategies for CVE-2025-59339 should focus on immediate code-level fixes to ensure the signing functionality operates correctly when configured. Organizations should implement comprehensive logging and monitoring of the osh-encrypt-rsync script to detect and alert on any failures in the signing process. The fix should include proper error handling that prevents silent failures and ensures that when signing is requested, it either succeeds or fails with appropriate error messages. Security teams should also implement periodic validation checks to verify that signed files maintain their signatures and that the signing process is functioning correctly. Additionally, the system should be configured with redundant verification mechanisms to cross-check the integrity of session recordings, and automated alerts should be established for any anomalies in the signing process. Organizations should consider implementing the ATT&CK technique T1566.002 for credential access and T1070.004 for indicator removal to detect potential tampering attempts in session recordings, ensuring that the security controls remain effective against sophisticated adversaries who might exploit this vulnerability to compromise audit trails and maintain persistence within the system.