CVE-2019-19944 in libIEC61850
Summary
by MITRE
In libIEC61850 1.4.0, BerDecoder_decodeUint32 in mms/asn1/ber_decode.c has an out-of-bounds read, related to intLen and bufPos.
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Analysis
by VulDB Data Team • 03/16/2024
The vulnerability identified as CVE-2019-19944 resides within the libIEC61850 library version 1.4.0, specifically within the BerDecoder_decodeUint32 function located in the mms/asn1/ber_decode.c file. This library serves as a critical component for implementing the IEC 61850 standard, which governs communication in substations and power systems. The flaw manifests as an out-of-bounds read condition that occurs during the decoding of ASN.1 BER (Basic Encoding Rules) encoded data structures, particularly when processing unsigned 32-bit integers. The vulnerability stems from improper validation of buffer positions and length calculations during the decoding process, creating a scenario where the application may attempt to read memory beyond the allocated buffer boundaries.
The technical implementation of this vulnerability involves the manipulation of intLen and bufPos variables within the BER decoding routine. When processing encoded data, the function fails to properly validate the relationship between the expected data length and the actual buffer position, allowing an attacker to craft malicious input that triggers the out-of-bounds memory access. This condition can be exploited through crafted ASN.1 encoded packets sent to systems utilizing the vulnerable library, potentially leading to information disclosure or application instability. The vulnerability is classified under CWE-129 as an "Improper Validation of Array Index" and represents a classic buffer over-read scenario that can be leveraged for information leakage or denial of service attacks.
From an operational standpoint, this vulnerability presents significant risks to industrial control systems and power grid infrastructure that rely on IEC 61850 compliant communication protocols. Systems utilizing the affected library may experience crashes or unpredictable behavior when processing malformed ASN.1 data, potentially leading to service disruption in critical infrastructure environments. The impact extends beyond simple application crashes as the out-of-bounds read could expose sensitive memory contents, including cryptographic keys, system credentials, or operational data that may be accessible through memory corruption. The vulnerability aligns with ATT&CK technique T1059.007 for application layer command injection and T1499.004 for network denial of service, as it can be leveraged to compromise system integrity and availability.
Mitigation strategies for CVE-2019-19944 primarily involve upgrading to a patched version of the libIEC61850 library where the buffer validation logic has been corrected. Organizations should implement network segmentation and monitoring to detect anomalous ASN.1 packet traffic that may indicate exploitation attempts. Additionally, input validation should be strengthened at all communication interfaces to filter malformed data before it reaches the vulnerable decoding functions. The fix typically involves proper bounds checking of buffer positions and length parameters, ensuring that intLen values are validated against available buffer space before memory access operations occur. Security teams should also consider implementing runtime protections such as address space layout randomization and stack canaries to reduce the exploitability of similar vulnerabilities in the broader codebase, aligning with defense-in-depth strategies recommended by NIST SP 800-53 and ISO/IEC 27001 standards for industrial control system security.