Remote Code Execution Vulnerability in IBM MQ (CVE-2026-12665)

IBM MQ is susceptible to a stack-based buffer overflow vulnerability, tracked as CVE-2026-12665, which can be triggered during the establishment of a channel connection. The vulnerability resides in the component responsible for processing TLS certificates. Specifically, when the application parses a certificate containing a malformed Distinguished Name (DN), it may overflow the stack buffer. Because this occurs during the early stages of a TLS handshake, a remote, unauthenticated attacker could potentially trigger this memory corruption by initiating a connection with a specially crafted certificate. Given the critical nature of messaging middleware in enterprise environments, successful exploitation could grant an attacker full control over the MQ process, leading to further internal network compromise or data exfiltration.

Impact

Successful exploitation of CVE-2026-12665 allows for unauthenticated remote code execution on the IBM MQ server. This poses a high risk to financial, logistics, and supply chain organizations that rely on IBM MQ for secure message queuing. If exploited, an attacker could intercept or manipulate sensitive business data, disable message processing, or use the compromised server as a pivot point into protected segments of the internal network.

Recommendation

• Patch IBM MQ installations to the version addressing CVE-2026-12665 immediately.
• Review TLS configurations and restrict allowed certificate issuers to trusted internal or external CAs to reduce the attack surface for malicious handshakes.
• Monitor network traffic logs for anomalous TLS handshake initiations or unusually large certificate field sizes directed toward IBM MQ listening ports.