CVE-2018-18480 in libopencad
Summary
by MITRE
A heap-based buffer over-read exists in libopencad 0.2.0 in the ReadMCHAR function in lib/dwg/io.cpp, resulting in an application crash.
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Analysis
by VulDB Data Team • 05/30/2023
The vulnerability identified as CVE-2018-18480 represents a critical heap-based buffer over-read flaw within the libopencad library version 0.2.0. This issue specifically manifests within the ReadMCHAR function located in the lib/dwg/io.cpp source file, where improper input validation leads to memory access violations that can compromise application stability and potentially enable further exploitation vectors. The affected library serves as a crucial component for handling CAD file formats, making this vulnerability particularly concerning for applications relying on proper binary parsing capabilities.
The technical implementation of this flaw stems from inadequate bounds checking during the processing of MCHAR (Multi-Character) data structures within CAD files. When the ReadMCHAR function attempts to read character data from memory locations, it fails to properly validate the size of the input buffer against the expected data length, resulting in memory access beyond allocated heap boundaries. This over-read condition occurs when the application processes malformed or intentionally crafted CAD files that contain oversized character sequences, causing the program to access memory regions that were not properly allocated for the intended operation. Such behavior directly aligns with CWE-125, which categorizes out-of-bounds read vulnerabilities as a fundamental memory safety issue that can lead to unpredictable application behavior and system instability.
The operational impact of this vulnerability extends beyond simple application crashes, as it creates potential pathways for denial-of-service attacks that can disrupt legitimate user workflows and system availability. When exploited, the heap-based buffer over-read can cause applications to terminate unexpectedly, leading to data loss and service interruption for users working with CAD files. The vulnerability's exploitation potential increases when considering that CAD applications often process files from untrusted sources, making this flaw particularly dangerous in environments where users might encounter maliciously crafted CAD files. Furthermore, the nature of heap corruption from such over-reads can potentially be leveraged in more sophisticated attacks, especially when combined with other memory corruption vulnerabilities within the same application stack.
Mitigation strategies for CVE-2018-18480 should prioritize immediate patching of affected libopencad installations to version 0.2.1 or later, which contains the necessary bounds checking fixes for the ReadMCHAR function. System administrators should implement strict input validation measures for all CAD file processing, including file format verification and size limitation controls that prevent processing of unusually large character sequences. Network security controls should include monitoring for suspicious file access patterns and implementing sandboxing techniques to isolate CAD processing environments from critical system resources. Additionally, organizations should conduct thorough vulnerability assessments of all applications utilizing libopencad to identify potential indirect impacts from this memory corruption issue, as the vulnerability may manifest differently across various software implementations that depend on the affected library. The ATT&CK framework categorizes this type of vulnerability under the 'Memory Injection' tactic, where adversaries may attempt to leverage buffer over-read conditions to achieve arbitrary code execution through memory corruption exploitation techniques.