CVE-2016-4354 in Libksba
Summary
by MITRE
ber-decoder.c in Libksba before 1.3.3 uses an incorrect integer data type, which allows remote attackers to cause a denial of service (crash) via crafted BER data, which leads to a buffer overflow.
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Analysis
by VulDB Data Team • 08/23/2022
The vulnerability identified as CVE-2016-4354 resides within the ber-decoder.c component of Libksba version 1.3.2 and earlier, representing a critical flaw in the handling of Basic Encoding Rules data structures. This issue stems from the improper use of integer data types during the decoding process, creating a scenario where malformed input can trigger unexpected behavior in the application's memory management systems. The vulnerability specifically affects the way the library processes binary data encoded using the Basic Encoding Rules standard, which is commonly used in cryptographic applications and certificate handling systems.
The technical root cause of this vulnerability manifests as an integer type mismatch that occurs when processing crafted BER data structures. When the library encounters malformed input, the incorrect data type handling leads to a buffer overflow condition where the application attempts to write data beyond the allocated memory boundaries. This memory corruption directly results in application crashes and can potentially be exploited to achieve more severe outcomes such as arbitrary code execution. The flaw demonstrates characteristics consistent with CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1499.004 related to network denial of service attacks through resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption, as it affects any application that relies on Libksba for certificate processing or cryptographic operations. Systems utilizing this library for email encryption, digital signature verification, or certificate management become vulnerable to remote exploitation by attackers who can craft malicious BER data to trigger the buffer overflow. The vulnerability's remote attack surface means that malicious actors can exploit it without requiring local access, making it particularly dangerous in networked environments where certificate processing occurs frequently. This affects a wide range of applications including email clients, security tools, and cryptographic libraries that depend on the affected library for proper functionality.
Mitigation strategies for CVE-2016-4354 primarily focus on upgrading to Libksba version 1.3.3 or later, which contains the necessary patches to correct the integer type handling in the ber-decoder.c file. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing affected versions of the library and prioritize remediation efforts accordingly. Additional defensive measures include implementing network segmentation to limit exposure, monitoring for suspicious BER data patterns, and establishing robust input validation mechanisms. The fix addresses the underlying integer type mismatch by ensuring proper data type handling during BER decoding operations, thereby preventing the buffer overflow condition that previously led to application crashes and potential exploitation opportunities. Security teams should also consider implementing automated patch management processes to ensure timely deployment of security updates across all affected systems.