CVE-2026-67873 in lib60870
Summary
by MITRE • 08/06/2026
A heap-based buffer overflow exists in lib60870-C 2.4.0 in the server-side FileSegment ASDU encoding path. The issue occurs because FileSegment_encode() validates only the standalone segment length via FileSegment_GetMaxDataSize() and does not verify the residual capacity of the current ASDU frame before encoding object fields and segment data
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Analysis
by VulDB Data Team • 08/06/2026
The heap-based buffer overflow vulnerability in lib60870-C version 2.4.0 represents a critical security flaw within the server-side implementation of the IEC 60870-5-104 communication protocol library. This vulnerability specifically manifests during FileSegment ASDU encoding operations where the software fails to properly validate buffer boundaries before writing data into memory structures. The issue stems from insufficient input validation mechanisms that allow maliciously crafted data to overwrite adjacent heap memory regions, potentially leading to arbitrary code execution or system instability.
The technical root cause of this vulnerability lies in the FileSegment_encode() function's incomplete validation approach. While the implementation correctly retrieves the maximum data size for individual segments using FileSegment_GetMaxDataSize(), it neglects to verify whether the current ASDU frame has sufficient remaining capacity to accommodate both the object fields and the segment data being encoded. This oversight creates a condition where the encoding process can write beyond allocated memory boundaries, particularly affecting heap-allocated buffers that store the serialized ASDU frames. The vulnerability follows CWE-121 heap-based buffer overflow patterns and aligns with ATT&CK technique T1059.007 for execution through memory corruption.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can be exploited by remote attackers to execute arbitrary code within the context of the affected application process. An attacker capable of sending specially crafted FileSegment ASDU messages could trigger the buffer overflow condition during normal protocol operation, potentially leading to complete system compromise. The attack surface includes any system running lib60870-C 2.4.0 that accepts FileSegment ASDU messages from untrusted sources, particularly industrial control systems and SCADA environments that rely on IEC 60870-5-104 protocol implementations.
Mitigation strategies should focus on immediate code-level fixes including comprehensive buffer validation before memory writes, implementing proper bounds checking in the FileSegment_encode() function, and ensuring that all data written to ASDU frames respects remaining capacity calculations. Organizations should prioritize upgrading to patched versions of lib60870-C where available, while implementing network segmentation and access controls to limit exposure. The vulnerability also highlights the importance of input validation testing and formal verification techniques in industrial protocol implementations, particularly those following ATT&CK framework's T1210 lateral movement patterns that could leverage such memory corruption exploits for further system compromise.