CVE-2020-28601 in libcgal
Summary
by MITRE • 03/05/2021
A code execution vulnerability exists in the Nef polygon-parsing functionality of CGAL libcgal CGAL-5.1.1. An oob read vulnerability exists in Nef_2/PM_io_parser.h PM_io_parser::read_vertex() Face_of[] OOB read. An attacker can provide malicious input to trigger this vulnerability.
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Analysis
by VulDB Data Team • 03/28/2021
The vulnerability CVE-2020-28601 represents a critical code execution flaw within the Computational Geometry Algorithms Library (CGAL) version 5.1.1, specifically within its Nef polygon-parsing component. This issue manifests as an out-of-bounds read condition in the PM_io_parser::read_vertex() function, which operates on a Face_of[] array structure. The vulnerability stems from insufficient input validation and boundary checking during the parsing of polygonal data structures, particularly when processing Nef polyhedra that represent planar maps with Boolean operations on polygons. The affected code path is typically triggered when the library attempts to parse malformed or maliciously crafted polygon data, creating a scenario where an attacker-controlled input can cause memory access violations that may be exploited for arbitrary code execution.
The technical implementation of this vulnerability involves the PM_io_parser class which handles input/output operations for Nef polyhedra, specifically within the Nef_2/PM_io_parser.h file. When processing vertex data, the read_vertex() method accesses a Face_of[] array without proper bounds checking, allowing an attacker to provide input that causes the parser to read beyond allocated memory boundaries. This out-of-bounds read occurs during the parsing of polygonal structures that define the topological relationships between faces, edges, and vertices in planar maps, which are fundamental to computational geometry operations. The vulnerability is classified as a CWE-125 Out-of-bounds Read according to the Common Weakness Enumeration catalog, and represents a classic memory safety issue that can lead to information disclosure, denial of service, or potentially remote code execution depending on the execution environment and memory layout.
The operational impact of this vulnerability extends across numerous applications that rely on CGAL for computational geometry operations, including CAD software, geographic information systems, computer graphics applications, and scientific computing tools. Attackers can exploit this vulnerability by crafting malicious polygonal input files that, when processed by the affected library, trigger the out-of-bounds memory access. The exploitability of this vulnerability depends on the execution context, but given that CGAL is widely used in applications that process user-provided geometric data, the attack surface is substantial. This vulnerability aligns with ATT&CK technique T1059.007 Command and Scripting Interpreter: PowerShell and similar techniques where malicious input can trigger code execution through library functions. The vulnerability affects systems where CGAL is used to parse polygonal data from untrusted sources, including web applications that accept geometric file uploads or desktop applications that process CAD files and geometric datasets.
Mitigation strategies for CVE-2020-28601 require immediate patching of affected CGAL installations to version 5.1.2 or later, which includes fixed boundary checking in the PM_io_parser::read_vertex() method. Organizations should implement input validation measures to sanitize all polygonal data before processing, particularly when the data originates from untrusted sources. Additionally, deployment of memory safety tools such as address sanitizers and static analysis scanners can help detect similar vulnerabilities in custom code that interfaces with CGAL. The fix implemented by the CGAL development team addresses the root cause by adding proper bounds checking to the Face_of[] array access, ensuring that vertex parsing operations cannot exceed allocated memory boundaries. System administrators should also consider implementing network segmentation and access controls to limit the impact of potential exploitation, particularly in environments where multiple applications depend on the same vulnerable library components. Regular security assessments and vulnerability scanning should be conducted to identify other potential memory safety issues in the broader software ecosystem that may be vulnerable to similar out-of-bounds access patterns.