CVE-2016-6303 in MySQL Workbench
Summary
by MITRE
Integer overflow in the MDC2_Update function in crypto/mdc2/mdc2dgst.c in OpenSSL before 1.1.0 allows remote attackers to cause a denial of service (out-of-bounds write and application crash) or possibly have unspecified other impact via unknown vectors.
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Analysis
by VulDB Data Team • 12/01/2022
The vulnerability identified as CVE-2016-6303 represents a critical integer overflow flaw within the MDC2 message digest algorithm implementation in OpenSSL versions prior to 1.1.0. This issue resides in the MDC2_Update function located in the crypto/mdc2/mdc2dgst.c source file, where improper handling of integer arithmetic leads to unpredictable behavior during cryptographic operations. The MDC2 algorithm, while deprecated in modern cryptographic standards, remains part of OpenSSL's legacy implementation and continues to be processed by systems that have not migrated to more secure alternatives.
The technical flaw manifests when the MDC2_Update function processes input data that triggers integer overflow conditions during internal counter calculations. This overflow results in an out-of-bounds write operation where the application attempts to write data beyond the allocated memory boundaries of the internal buffer used for cryptographic processing. Such memory corruption directly leads to application crashes and potential denial of service conditions that can be exploited remotely by attackers who can craft specific input sequences to trigger the vulnerable code path.
From an operational impact perspective, this vulnerability presents significant risks to systems relying on OpenSSL for cryptographic operations, particularly those that may still utilize MDC2 functionality for legacy compatibility or backward compatibility reasons. The remote exploitation capability means that attackers can potentially cause service disruption without requiring local access or authentication, making this a particularly dangerous vulnerability in network-facing applications. The unspecified other impacts mentioned in the CVE description suggest potential for more severe consequences including information disclosure or privilege escalation depending on the execution environment and system configuration.
The vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions, and demonstrates characteristics consistent with the ATT&CK technique T1499.004 for Network Denial of Service. Organizations should prioritize immediate migration to OpenSSL 1.1.0 or later versions where this vulnerability has been resolved through proper integer boundary checking and overflow prevention mechanisms. Additionally, system administrators should conduct comprehensive audits of their cryptographic library usage to identify any remaining dependencies on deprecated algorithms like MDC2 that may expose systems to similar vulnerabilities.
Mitigation strategies should include immediate patching of OpenSSL installations to versions 1.1.0 or higher, implementation of network segmentation to limit exposure of vulnerable systems, and thorough code review processes to identify potential integer overflow conditions in custom cryptographic implementations. Regular vulnerability assessments and security monitoring should be maintained to detect any attempts to exploit this or similar vulnerabilities in the cryptographic infrastructure. The resolution of this issue demonstrates the importance of proper integer overflow handling in cryptographic libraries and reinforces the necessity of keeping cryptographic software updated to protect against known vulnerabilities that could compromise system availability and integrity.