CVE-2020-21535 in fig2dev
Summary
by MITRE • 09/17/2021
fig2dev 3.2.7b contains a segmentation fault in the gencgm_start function in gencgm.c.
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Analysis
by VulDB Data Team • 09/22/2021
The vulnerability identified as CVE-2020-21535 affects the fig2dev tool version 3.2.7b, which is part of the netpbm package used for converting figure files to various formats. This particular issue manifests as a segmentation fault within the gencgm_start function located in the gencgm.c source file, representing a critical memory access violation that can lead to application crashes and potential system instability. The flaw occurs during the processing of figure files when the application attempts to access memory locations that have not been properly allocated or are otherwise inaccessible, creating a scenario where legitimate input can trigger unexpected program termination.
The technical implementation of this vulnerability stems from inadequate input validation and memory management within the CGM (Computer Graphics Metafile) generation component of fig2dev. When the gencgm_start function processes certain malformed or specially crafted figure files, it fails to properly handle boundary conditions and memory allocation checks, leading to a segmentation fault that terminates the application process. This type of vulnerability falls under the CWE-125 vulnerability category, which describes out-of-bounds read conditions where an application accesses memory beyond the boundaries of a valid buffer. The flaw demonstrates characteristics of CWE-787, out-of-bounds write vulnerabilities, as the improper memory handling can potentially allow attackers to manipulate memory locations beyond intended boundaries.
The operational impact of CVE-2020-21535 extends beyond simple application crashes, as it represents a potential denial of service vulnerability that can be exploited by malicious actors to disrupt services relying on fig2dev functionality. Systems that process figure files through this tool, particularly those in automated workflows, web applications, or document processing environments, may become vulnerable to service disruption when attackers submit specially crafted input files. The vulnerability aligns with ATT&CK technique T1499.004, "Utilities: Endpoint Denial of Service," as it enables adversaries to cause system instability through targeted input manipulation. Additionally, this flaw could be leveraged in broader attack chains where attackers might attempt to exploit similar memory corruption vulnerabilities to achieve privilege escalation or code execution, particularly in environments where fig2dev is used in security-sensitive contexts.
Mitigation strategies for CVE-2020-21535 should prioritize immediate patching of affected systems to version 3.2.7c or later, which contains the necessary memory management fixes and input validation improvements. Organizations should implement input sanitization measures to filter potentially malicious figure files before processing, particularly in web-facing applications where user-submitted content is processed. The implementation of sandboxing techniques for figure file processing can help contain potential exploits within isolated environments, preventing broader system compromise. Additionally, monitoring and logging of fig2dev usage can help detect anomalous processing patterns that might indicate exploitation attempts. System administrators should also consider implementing network segmentation and access controls to limit exposure of systems running vulnerable versions of fig2dev, particularly in environments where automated processing of user-generated content occurs. Regular security assessments and vulnerability scanning should be conducted to identify similar memory corruption issues in other components of the netpbm suite or similar graphics processing tools.