CVE-2016-4579 in Libksba
Summary
by MITRE
Libksba before 1.3.4 allows remote attackers to cause a denial of service (out-of-bounds read and crash) via unspecified vectors, related to the "returned length of the object from _ksba_ber_parse_tl."
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/23/2022
The vulnerability identified as CVE-2016-4579 affects the libksba library version 1.3.4 and earlier, representing a critical security flaw that enables remote attackers to execute denial of service attacks through out-of-bounds memory read operations. This vulnerability specifically manifests within the ksba_ber_parse_tl function, which handles the parsing of ber encoded data structures commonly used in cryptographic applications. The flaw occurs when the library processes malformed or specially crafted input data that causes the parsing routine to read memory locations beyond the allocated buffer boundaries, resulting in unpredictable program behavior and potential system crashes.
The technical implementation of this vulnerability stems from inadequate bounds checking within the ber parsing mechanism of libksba. When the _ksba_ber_parse_tl function encounters certain malformed data sequences, it fails to properly validate the length parameters returned during the parsing process. This allows attackers to manipulate the data flow such that memory access operations extend beyond the intended buffer limits, creating conditions that lead to segmentation faults and application termination. The vulnerability operates at the protocol parsing layer, making it particularly dangerous as it can be triggered through any application that relies on libksba for handling x509 certificates or other ber encoded cryptographic objects.
The operational impact of CVE-2016-4579 extends beyond simple service disruption, as it represents a fundamental memory safety issue that can be exploited across multiple applications depending on libksba. Systems that utilize this library for certificate processing, email encryption, or digital signature verification become vulnerable to remote exploitation, potentially affecting email servers, certificate authorities, and cryptographic tools. The out-of-bounds read conditions can also provide attackers with information disclosure opportunities, as reading beyond buffer boundaries may expose sensitive data from adjacent memory locations. This vulnerability aligns with CWE-129, which addresses improper validation of length parameters, and falls under the broader category of memory safety issues that have been extensively documented in security frameworks.
Mitigation strategies for this vulnerability require immediate patching of affected systems to upgrade to libksba version 1.3.4 or later, which contains the necessary fixes for the bounds checking implementation. Network administrators should prioritize this update across all systems that utilize the vulnerable library, particularly those handling cryptographic operations or processing external certificate data. Additional defensive measures include implementing proper input validation at application layers that use libksba, deploying intrusion detection systems to monitor for exploitation attempts, and configuring application sandboxing to limit the impact of potential crashes. The remediation process should also involve comprehensive vulnerability scanning to identify all systems that may be affected by this dependency, as libksba is commonly used in various cryptographic toolchains and email systems that may not be immediately apparent. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and prevent similar vulnerabilities from remaining unpatched in their environments.