CVE-2020-28615 in CGAL
Summary
by MITRE • 04/18/2022
Multiple code execution vulnerabilities exists in the Nef polygon-parsing functionality of CGAL libcgal CGAL-5.1.1. A specially crafted malformed file can lead to an out-of-bounds read and type confusion, which could lead to code execution. An attacker can provide malicious input to trigger any of these vulnerabilities. An oob read vulnerability exists in Nef_S2/SNC_io_parser.h SNC_io_parser<EW>::read_vertex() vh->shalfedges_last().
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Analysis
by VulDB Data Team • 04/18/2022
The vulnerability described represents a critical code execution risk within the Computational Geometry Algorithms Library CGAL version 5.1.1, specifically affecting the polygon-parsing functionality used for Nef operations. This issue stems from improper input validation and memory management within the SNC_io_parser class, which handles the parsing of geometric data structures. The vulnerability manifests through multiple attack vectors including out-of-bounds read conditions and type confusion errors that can be exploited to achieve arbitrary code execution. The root cause lies in the insufficient bounds checking during vertex parsing operations, particularly in the read_vertex() method of the SNC_io_parser template class.
The technical flaw occurs when processing malformed input files through the Nef_S2/SNC_io_parser.h component, specifically within the SNC_io_parser::read_vertex() function where the vulnerability is triggered by accessing vh->shalfedges_last() without proper validation of array boundaries. This out-of-bounds read creates a type confusion scenario that can be leveraged by attackers to manipulate memory layout and potentially execute malicious code. The vulnerability is classified as a CWE-125 Out-of-bounds Read and CWE-476 Null Pointer Dereference, both of which are well-documented in the Common Weakness Enumeration catalog and represent significant security risks in software libraries handling external data inputs.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a pathway to execute arbitrary code within the context of applications using CGAL's Nef functionality. This affects any software that relies on CGAL for computational geometry operations, including CAD systems, geographic information systems, computer graphics applications, and scientific computing platforms. The vulnerability is particularly concerning because it can be triggered through seemingly innocuous input files, making it difficult to detect and prevent in production environments. Attackers can craft malicious polygon files that, when processed by vulnerable applications, will trigger the memory corruption leading to code execution.
Mitigation strategies should focus on immediate input validation and bounds checking within the affected parsing functions, with comprehensive testing of all external data sources before processing. The recommended approach includes implementing strict validation of polygon data structures, adding defensive programming measures such as array boundary checks, and employing memory safety techniques like address sanitization. Organizations should also consider applying patches or upgrading to versions of CGAL that have addressed these vulnerabilities, while implementing runtime protections such as stack canaries and control flow integrity checks. From an ATT&CK framework perspective, this vulnerability maps to T1059 Command and Scripting Interpreter and T1555 Credential Access, as the successful exploitation could lead to complete system compromise. The vulnerability demonstrates the critical importance of validating all external inputs in security-sensitive libraries and highlights the need for comprehensive testing of parsing functions in computational geometry software to prevent similar issues in other mathematical libraries.