CVE-2020-18032 in Graph Visualization Tools
Summary
by MITRE • 04/30/2021
Buffer Overflow in Graphviz Graph Visualization Tools from commit ID f8b9e035 and earlier allows remote attackers to execute arbitrary code or cause a denial of service (application crash) by loading a crafted file into the "lib/common/shapes.c" component.
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Analysis
by VulDB Data Team • 11/24/2025
The vulnerability identified as CVE-2020-18032 represents a critical buffer overflow flaw within the Graphviz graph visualization software suite that affects versions prior to commit f8b9e035. This issue resides within the lib/common/shapes.c component of the software, which is responsible for handling various graph shapes and their rendering capabilities. The buffer overflow occurs when the application processes specially crafted input files that contain malformed data structures, particularly those related to graph shape definitions and their associated attributes. The flaw stems from insufficient bounds checking during the parsing of input data, allowing attackers to overwrite adjacent memory locations with malicious content.
The technical exploitation of this vulnerability follows a classic buffer overflow pattern where an attacker can manipulate the memory layout of the application by providing input that exceeds the allocated buffer size. When Graphviz attempts to parse and render a crafted graph file, the insufficient validation in shapes.c permits data to be written beyond the intended memory boundaries. This condition creates opportunities for arbitrary code execution if the attacker can control the overwritten memory locations or trigger a denial of service through application crashes. The vulnerability is particularly concerning because it can be triggered through legitimate file loading operations, making it accessible to remote attackers who can deliver malicious files via web downloads, email attachments, or other delivery mechanisms.
From an operational impact perspective, this vulnerability poses significant risks to organizations that rely on Graphviz for diagram generation, documentation, or visualization purposes. The potential for remote code execution means that attackers could gain full control over systems running vulnerable Graphviz versions, especially when these tools are used in web applications, automated documentation systems, or collaborative environments where users might encounter malicious graph files. The denial of service aspect further compounds the risk as attackers could disrupt services by causing application crashes, leading to availability issues that impact business operations. The vulnerability affects not only direct users of Graphviz but also applications that integrate Graphviz as a visualization backend, creating a broader attack surface.
Mitigation strategies for CVE-2020-18032 should prioritize immediate patching of affected Graphviz installations to versions that include the fix from commit f8b9e035 or later. Organizations should implement input validation measures and restrict file upload capabilities in web applications that utilize Graphviz to prevent processing untrusted graph files. Network segmentation and access controls can help limit the potential impact if exploitation occurs, while monitoring systems should be deployed to detect unusual processing patterns or crashes that might indicate exploitation attempts. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a technique that could be categorized under ATT&CK tactic TA0002 (Execution) and technique T1059.007 (Command and Scripting Interpreter: PowerShell). Additionally, organizations should consider implementing application whitelisting policies and regular security assessments to identify similar vulnerabilities in other visualization and graph processing tools that may be present in their infrastructure.