CVE-2026-63550 in libiec61850
Summary
by MITRE • 07/31/2026
The MMS BER decoder contains a boundary-handling flaw in the processing of certain fields within confirmed-request messages. When a crafted BER-encoded element is received over an established MMS session (TCP port 102), the decoder may advance its internal read position incorrectly, leading to a heap out-of-bounds read. This condition causes the MMS handling process to terminate unexpectedly, resulting in a denial-of-service.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 07/31/2026
The vulnerability resides within the MMS (Manufacturing Message Specification) protocol implementation where the Basic Encoding Rules (BER) decoder demonstrates improper boundary handling during confirmed-request message processing. This issue manifests when the system receives crafted BER-encoded elements over TCP port 102, which serves as the standard communication port for MMS protocols. The flaw specifically impacts how the decoder manages internal read position tracking when processing certain field structures within these messages. When encountering malformed BER encodings, the decoder fails to properly validate boundary conditions, causing it to advance its internal pointer beyond allocated memory boundaries.
The technical execution of this vulnerability involves a heap out-of-bounds read condition that occurs during the decoding process of MMS confirmed-request messages. The improper boundary handling allows an attacker to manipulate the decoder's internal state by sending specially crafted BER elements that cause the read position pointer to reference memory locations outside the intended buffer boundaries. This memory access violation triggers an unexpected termination of the MMS handling process, creating a denial-of-service condition that affects the entire communication session.
From an operational impact perspective, this vulnerability represents a significant security concern for industrial control systems and manufacturing environments that rely on MMS protocols for device communication and data exchange. The denial-of-service condition effectively disrupts normal operations by terminating the MMS handling process, which can lead to complete communication breakdowns between industrial devices and control systems. This vulnerability is particularly concerning in critical infrastructure environments where continuous operation is essential, as the service disruption can cascade through connected systems and potentially impact production processes.
The flaw aligns with CWE-129: Improper Validation of Array Index and CWE-787: Out-of-bounds Write or Read categories from the Common Weakness Enumeration catalog. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1499.004: Endpoint Denial of Service within the Network Denial of Service sub-technique, as it specifically targets the availability aspect of industrial communication protocols. The vulnerability demonstrates a classic buffer over-read condition that can be exploited through network-based attacks without requiring privileged access or authentication.
Mitigation strategies should focus on implementing proper input validation and boundary checking within the BER decoder implementation. Organizations should deploy network segmentation to limit access to TCP port 102 to authorized systems only, implement intrusion detection systems to monitor for suspicious MMS traffic patterns, and ensure regular firmware updates from vendors addressing this specific memory handling flaw. Additionally, defensive measures including rate limiting of incoming MMS connections and implementing robust error handling that prevents process termination upon malformed input should be considered to reduce the attack surface and improve system resilience against similar boundary condition vulnerabilities.