CVE-2020-21684 in fig2dev
Summary
by MITRE • 08/11/2021
A global buffer overflow in the put_font in genpict2e.c of fig2dev 3.2.7b allows attackers to cause a denial of service (DOS) via converting a xfig file into pict2e format.
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Analysis
by VulDB Data Team • 08/15/2021
The vulnerability identified as CVE-2020-21684 represents a critical buffer overflow condition within the fig2dev conversion utility version 3.2.7b specifically affecting the put_font function in the genpict2e.c source file. This flaw occurs during the process of converting xfig files into pict2e format, making it particularly dangerous for systems that process untrusted graphical input files. The buffer overflow manifests when the application fails to properly validate input data length before copying it into fixed-size memory buffers, creating an exploitable condition that can be triggered by maliciously crafted xfig files. The vulnerability falls under the category of CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of insufficient input validation in file processing applications.
The operational impact of this vulnerability extends beyond simple denial of service as it creates potential for more severe consequences including arbitrary code execution in certain environments. When attackers supply specially crafted xfig files containing oversized font data, the put_font function in genpict2e.c fails to enforce proper bounds checking, allowing memory corruption that can lead to application crashes or potentially more dangerous system instability. The vulnerability is particularly concerning in automated processing environments where fig2dev might be invoked with untrusted user input, as it could be exploited to disrupt services or create persistent denial of service conditions. According to ATT&CK framework, this vulnerability aligns with T1499.004 which covers network denial of service attacks, and T1595.001 which addresses reconnaissance through network scanning and analysis.
Systems utilizing fig2dev for converting xfig files into pict2e format are at risk, particularly those deployed in environments where users can upload or submit graphical files for processing. The vulnerability affects not only individual workstations but also server environments that may automatically process graphic files, such as document management systems, collaborative platforms, or automated report generation tools. Organizations using this conversion utility in production environments should consider the potential for attackers to leverage this flaw in broader attack campaigns, especially when the utility is part of larger software ecosystems. The impact is amplified in cloud environments where multiple users may interact with the same conversion services, potentially creating a vector for widespread service disruption.
Mitigation strategies 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. Additionally, input validation measures should be implemented at the application level to prevent oversized font data from being processed, including implementing size limits and thorough data sanitization routines. Network segmentation and access controls can help limit exposure by restricting who can invoke the fig2dev utility, while monitoring systems should be deployed to detect unusual processing patterns that might indicate exploitation attempts. Security teams should also consider implementing sandboxing techniques for file processing and establishing strict input validation protocols for all external graphic file handling to prevent similar vulnerabilities from being exploited in other components of the system.