CVE-2020-21682 in fig2dev
Summary
by MITRE • 08/11/2021
A global buffer overflow in the set_fill component in genge.c of fig2dev 3.2.7b allows attackers to cause a denial of service (DOS) via converting a xfig file into ge format.
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Analysis
by VulDB Data Team • 06/26/2025
The vulnerability identified as CVE-2020-21682 represents a critical buffer overflow condition within the fig2dev conversion utility version 3.2.7b. This issue specifically affects the set_fill component located in the genge.c source file, which is responsible for processing xfig files and converting them into ge format. The buffer overflow occurs during the handling of input data from xfig files, creating a scenario where attacker-controlled data can overwrite adjacent memory regions beyond the allocated buffer boundaries. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, where insufficient bounds checking allows for memory corruption that can lead to unpredictable behavior.
The technical exploitation of this vulnerability requires an attacker to craft a malicious xfig file that triggers the buffer overflow when processed by fig2dev during the conversion to ge format. When the set_fill component processes malformed input data, it fails to properly validate the size of incoming data against the allocated buffer space, allowing for arbitrary data to overwrite adjacent memory locations. This memory corruption can result in application crashes, segmentation faults, or potentially more severe consequences depending on the memory layout and the specific nature of the overflow. The vulnerability is particularly concerning because it can be triggered through normal file conversion operations, making it accessible to unauthenticated attackers who can simply provide a specially crafted xfig file to the application.
From an operational perspective, this buffer overflow vulnerability creates a significant denial of service risk for systems that rely on fig2dev for graphic file conversions. Organizations using this utility in automated workflows, web applications, or file processing pipelines may experience system instability or complete service interruption when processing malicious input files. The vulnerability can be exploited in various contexts including web applications that accept xfig file uploads, automated document conversion services, or any system where fig2dev is used to process user-provided graphics files. The impact extends beyond simple service disruption as the memory corruption could potentially lead to more severe consequences if the overflow affects critical program structures or if it can be chained with other vulnerabilities to achieve arbitrary code execution.
The mitigation strategies for CVE-2020-21682 should focus on immediate patching of the fig2dev utility to version 3.2.7c or later, which contains the necessary fixes for the buffer overflow condition. Organizations should also implement input validation measures to restrict the types of xfig files that can be processed, including size limitations and format validation checks. Additionally, deployment of application sandboxing techniques and restricted execution environments can help contain the impact of potential exploitation attempts. Security monitoring should be enhanced to detect unusual file conversion patterns or attempts to process malformed input files that could indicate exploitation attempts. The vulnerability demonstrates the importance of proper bounds checking and input validation in preventing buffer overflow attacks, aligning with ATT&CK technique T1203 for legitimate credential use and T1059 for command and scripting interpreter usage that could be employed in exploitation scenarios. Organizations should also consider implementing network segmentation and access controls to limit exposure of systems running fig2dev to trusted users only, reducing the attack surface available to potential adversaries.