CVE-2017-6350 in VIM
Summary
by MITRE
An integer overflow at an unserialize_uep memory allocation site would occur for vim before patch 8.0.0378, if it does not properly validate values for tree length when reading a corrupted undo file, which may lead to resultant buffer overflows.
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Analysis
by VulDB Data Team • 08/18/2020
The vulnerability identified as CVE-2017-6350 represents a critical integer overflow flaw within the vim text editor software that existed prior to patch version 8.0.0378. This issue manifests during the deserialization process when vim attempts to read corrupted undo files, specifically within the unserialize_uep memory allocation function. The flaw stems from inadequate input validation mechanisms that fail to properly check tree length values during undo file processing, creating a scenario where maliciously crafted undo files could trigger unexpected memory behavior. The vulnerability operates at the intersection of memory management and data serialization, making it particularly dangerous as it can be exploited through file-based attacks without requiring network connectivity.
The technical exploitation of this vulnerability occurs when vim processes undo files that contain malformed tree length values, causing integer overflow conditions during memory allocation calculations. When the system attempts to allocate memory based on these invalid values, it can result in insufficient memory allocation or incorrect buffer sizing, leading to subsequent buffer overflow conditions. This type of vulnerability falls under the CWE-190 category of integer overflow, specifically manifesting as an overflow during memory allocation operations. The flaw represents a classic example of how improper input validation during deserialization can lead to memory corruption vulnerabilities, making it particularly susceptible to exploitation through crafted file inputs.
The operational impact of CVE-2017-6350 extends beyond simple denial of service conditions, as the buffer overflow potential creates opportunities for arbitrary code execution within the context of the vim process. Attackers could potentially craft malicious undo files that, when opened by an unsuspecting user, would trigger the overflow condition and allow for privilege escalation or system compromise. The vulnerability affects the core functionality of vim's undo file handling mechanism, which is frequently used during text editing operations, making it a high-value target for exploitation. This type of vulnerability aligns with ATT&CK technique T1203 - Exploitation for Client Execution, as it leverages file-based attack vectors to execute malicious code through legitimate software applications.
Mitigation strategies for CVE-2017-6350 primarily focus on applying the official patch version 8.0.0378 which addresses the integer overflow condition through proper input validation of tree length values during undo file processing. System administrators should ensure all vim installations are updated to the patched versions to eliminate the vulnerability. Additionally, implementing proper file validation procedures and restricting access to undo files from untrusted sources can provide additional defense layers. Organizations should also consider implementing application whitelisting policies that restrict the execution of vulnerable versions of vim and monitor for suspicious undo file access patterns. The vulnerability demonstrates the importance of robust input validation in memory management operations and highlights the necessity of comprehensive testing for integer overflow conditions in serialization functions, particularly in widely-used software applications that handle user-provided data.