CVE-2020-14315 in bsdiff
Summary
by MITRE
A memory corruption vulnerability is present in bspatch as shipped in Colin Percival’s bsdiff tools version 4.3. Insufficient checks when handling external inputs allows an attacker to bypass the sanity checks in place and write out of a dynamically allocated buffer boundaries.
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Analysis
by VulDB Data Team • 09/16/2020
The vulnerability identified as CVE-2020-14315 resides within the bspatch component of Colin Percival's bsdiff tools version 4.3, representing a critical memory corruption flaw that fundamentally compromises the integrity of the software's input processing mechanisms. This vulnerability manifests as a classic buffer overflow condition that occurs when the application fails to properly validate external inputs during patch file processing, creating a pathway for malicious actors to manipulate memory layout and execute arbitrary code. The flaw specifically targets the dynamic buffer management system where the application allocates memory based on input parameters without adequate boundary checking, allowing attackers to write beyond allocated memory boundaries and potentially overwrite adjacent memory structures.
The technical implementation of this vulnerability stems from insufficient validation routines within the bspatch utility's input parsing logic, where the tool processes binary patch files using a diff/patch algorithm that requires precise memory management. When processing malformed or specially crafted input data, the application fails to verify that input parameters such as patch offsets, sizes, and data lengths remain within expected bounds, leading to an out-of-bounds write condition that can be exploited to overwrite critical program memory. This issue aligns with CWE-121, which describes heap-based buffer overflow conditions, and more specifically maps to CWE-787, representing out-of-bounds write vulnerabilities that occur when an application writes to memory beyond the boundaries of a buffer. The vulnerability operates at the intersection of memory management and input validation, creating a scenario where legitimate input processing becomes a vector for memory corruption attacks.
The operational impact of CVE-2020-14315 extends beyond simple denial of service conditions to encompass potential remote code execution capabilities, particularly when the bspatch utility is executed in environments where it processes untrusted input from external sources. Attackers can craft malicious patch files that, when processed by vulnerable versions of bspatch, will trigger the buffer overflow condition and potentially allow for arbitrary code execution with the privileges of the user running the application. This vulnerability is particularly concerning in automated patching systems, software distribution networks, or any environment where bspatch is used to apply updates to systems, as it creates opportunities for attackers to inject malicious code into legitimate software update processes. The vulnerability's exploitation aligns with ATT&CK technique T1059.007, which covers command and script injection, and T1203, representing legitimate program execution, as attackers can leverage this flaw to execute malicious payloads through the patch application process.
Mitigation strategies for CVE-2020-14315 require immediate patching of affected systems to upgrade to versions of bsdiff tools that have addressed the memory corruption vulnerability through proper input validation and boundary checking mechanisms. Organizations should implement strict input validation policies for any patch files processed through bspatch, including signature verification and sandboxed processing environments to limit potential damage from exploitation attempts. The vulnerability's remediation should include comprehensive testing of patch processing workflows to ensure that all input parameters are properly validated before memory allocation occurs, preventing the conditions that allow for out-of-bounds writes. Additionally, system administrators should consider implementing network segmentation and access controls to limit exposure of systems running vulnerable versions of bspatch, while monitoring for anomalous patch processing activities that could indicate exploitation attempts. The fix for this vulnerability typically involves implementing proper bounds checking in buffer allocation routines and ensuring that all external inputs are validated against expected parameter ranges before memory operations are performed, addressing both the immediate memory corruption issue and the underlying validation deficiencies that enabled the exploit.