CVE-2020-21676 in fig2dev
Summary
by MITRE • 08/11/2021
A stack-based buffer overflow in the genpstrx_text() component in genpstricks.c of fig2dev 3.2.7b allows attackers to cause a denial of service (DOS) via converting a xfig file into pstricks format.
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Analysis
by VulDB Data Team • 08/15/2021
The vulnerability CVE-2020-21676 represents a stack-based buffer overflow affecting the fig2dev tool version 3.2.7b, specifically within the genpstricks.c source file in the genpstrx_text() function. This flaw occurs during the conversion process when xfig files are transformed into pstricks format, creating a critical security risk that can be exploited by malicious actors. The buffer overflow vulnerability arises from insufficient input validation and bounds checking within the text processing component of the fig2dev utility.
The technical implementation of this vulnerability stems from improper handling of string data within the genpstrx_text() function, where attacker-controlled input from xfig files can cause stack memory corruption. When processing certain malformed text elements in xfig files, the function fails to properly validate the length of input strings before copying them into fixed-size buffers on the stack. This classic buffer overflow condition allows attackers to overwrite adjacent stack memory locations, potentially leading to arbitrary code execution or system crashes. The vulnerability is classified as a CWE-121 stack-based buffer overflow, which directly maps to the ATT&CK technique T1059.007 for command and scripting interpreter execution through malformed input processing.
From an operational impact perspective, this vulnerability enables attackers to achieve denial of service conditions by causing the fig2dev application to crash or behave unpredictably during file conversion operations. The attack requires minimal privileges as the vulnerability exists within a utility that processes user-supplied input files, making it particularly dangerous in environments where automated file conversion services are deployed. The vulnerability can be exploited through specially crafted xfig files that contain oversized text elements, which when processed by fig2dev trigger the buffer overflow condition. This makes the vulnerability particularly concerning for web applications or automated systems that accept and process xfig file uploads without proper validation.
Effective mitigation strategies for CVE-2020-21676 involve immediate application of vendor patches and updates to fig2dev version 3.2.7c or later, which contain the necessary fixes for the buffer overflow condition. System administrators should implement input validation measures that restrict the size and format of xfig files processed by fig2dev applications, particularly in automated environments. Additionally, deployment of runtime protections such as stack canaries and address space layout randomization can provide additional defense-in-depth measures. Organizations should also consider implementing sandboxing techniques when processing untrusted xfig files to limit the potential impact of successful exploitation attempts. The vulnerability demonstrates the importance of proper input validation and bounds checking in file processing utilities, particularly those handling complex format conversions that involve multiple data transformation steps.