CVE-2018-3976 in Canvas Draw
Summary
by MITRE
An exploitable out-of-bounds write exists in the CALS Raster file format-parsing functionality of Canvas Draw version 5.0.0.28. A specially crafted CAL image processed via the application can lead to an out-of-bounds write, overwriting arbitrary data. An attacker can deliver a CAL image to trigger this vulnerability and gain code execution.
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Analysis
by VulDB Data Team • 07/06/2023
The vulnerability identified as CVE-2018-3976 represents a critical out-of-bounds write flaw within the CALS raster file format parsing mechanism of Canvas Draw version 5.0.0.28. This issue falls under the category of memory corruption vulnerabilities that can potentially lead to arbitrary code execution. The CALS raster format is a standard for storing raster graphics data, commonly used in technical drawing and document imaging applications. When Canvas Draw processes a specially crafted CAL image file, the application fails to properly validate the bounds of memory operations during file parsing, creating an exploitable condition. The vulnerability stems from inadequate input validation and boundary checking within the raster processing code that handles CALS format files.
The technical implementation of this vulnerability involves the application's handling of malformed CAL raster data structures that cause memory operations to exceed allocated buffer boundaries. When parsing the malicious CAL file, the parsing routine fails to verify array indices or buffer limits before writing data to memory locations. This flaw allows an attacker to craft a CAL image file that, when opened by Canvas Draw, triggers an out-of-bounds write condition. The memory corruption occurs during the raster data interpretation phase where the application attempts to write pixel or color information beyond the intended memory allocation. The vulnerability is particularly dangerous because it enables attackers to overwrite adjacent memory regions, potentially corrupting critical program data or even injecting executable code. This type of vulnerability is classified as CWE-787 Out-of-bounds Write within the Common Weakness Enumeration framework, which specifically addresses memory safety issues in software applications.
The operational impact of CVE-2018-3976 extends beyond simple memory corruption, as it provides a pathway for full system compromise. An attacker who successfully exploits this vulnerability can achieve arbitrary code execution within the context of the Canvas Draw application, potentially leading to complete system compromise. The attack vector requires the victim to open a malicious CAL file, making this a typical social engineering target that relies on user interaction. This vulnerability affects organizations that rely on Canvas Draw for document processing and technical drawing tasks, particularly those in engineering, architecture, or manufacturing sectors. The exploitability of this flaw is enhanced by the fact that CALS files are legitimate document formats that users may encounter in normal business operations, making detection and prevention more challenging. According to ATT&CK framework, this vulnerability maps to T1203 Exploitation for Client Execution, as it leverages a client-side application to execute malicious code.
Mitigation strategies for CVE-2018-3976 should focus on both immediate defensive measures and long-term architectural improvements. Organizations should immediately apply available patches from the software vendor to address the memory boundary checking issues in the CALS file parser. Until patches are applied, users should avoid opening untrusted CAL files or implement strict file validation procedures before processing raster graphics. Network-based mitigations could include content filtering that blocks or quarantines suspicious CAL files, while endpoint protection solutions should monitor for unusual memory access patterns during file processing. Security teams should also consider implementing application whitelisting policies that restrict execution of Canvas Draw to trusted environments. The vulnerability highlights the importance of proper input validation and memory safety practices in software development, particularly for applications that process external file formats. Organizations should conduct thorough security assessments of their document processing pipelines and implement defense-in-depth strategies that include runtime monitoring, sandboxing, and regular security updates to prevent exploitation of similar vulnerabilities in the future.