CVE-2020-21531 in fig2dev
Summary
by MITRE • 09/17/2021
fig2dev 3.2.7b contains a global buffer overflow in the conv_pattern_index function in gencgm.c.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/22/2021
The vulnerability CVE-2020-21531 represents a critical global buffer overflow flaw within the fig2dev conversion utility version 3.2.7b, specifically within the conv_pattern_index function located in the gencgm.c source file. This issue arises during the processing of FIG (Frame Interchange Format) files and manifests when the software attempts to convert these graphics files into CGM (Computer Graphics Metafile) format. The buffer overflow occurs due to insufficient bounds checking when handling pattern index data structures during the conversion process, creating a potential avenue for arbitrary code execution.
The technical implementation of this vulnerability stems from improper memory management practices within the conv_pattern_index function, which processes pattern index values without adequate validation of input boundaries. When maliciously crafted FIG files are processed through fig2dev, the function fails to verify that pattern index values remain within allocated memory boundaries, allowing attackers to overwrite adjacent memory locations. This flaw directly maps to CWE-121, which describes stack-based buffer overflow conditions where insufficient boundary checks permit memory corruption. The vulnerability can be exploited through the manipulation of pattern index parameters in FIG files, making it particularly dangerous in environments where users process untrusted graphics content.
The operational impact of this vulnerability extends beyond simple memory corruption, as it enables potential remote code execution attacks when fig2dev is used in automated processing environments or web applications. Attackers can craft specially designed FIG files that trigger the buffer overflow, potentially allowing them to execute arbitrary code with the privileges of the user running fig2dev. This presents significant risks in server environments where automatic conversion of user-uploaded graphics files occurs, as demonstrated by the ATT&CK technique T1059.007 for command and scripting interpreter execution. The vulnerability affects systems where fig2dev is installed and actively processing graphics files, particularly in automated workflows or web applications that utilize the utility for format conversion.
Mitigation strategies for CVE-2020-21531 should prioritize immediate patching of fig2dev to version 3.2.7c or later, which contains the necessary memory boundary checks and input validation fixes. Organizations should implement strict input validation procedures for all graphics files processed through fig2dev, including automated scanning for potentially malicious patterns in FIG file structures. Network segmentation and privilege separation can help limit the impact if exploitation occurs, while monitoring systems should be deployed to detect unusual processing patterns or file conversions that might indicate attempted exploitation. The fix implemented in the patched version addresses the root cause by introducing proper bounds checking in the conv_pattern_index function, preventing the overflow condition while maintaining the utility's legitimate functionality. System administrators should also consider disabling automatic conversion of untrusted graphics files and implementing sandboxing techniques to isolate the fig2dev process from critical system resources.