CVE-2020-28634 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::read_sedge() seh->next().
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Analysis
by VulDB Data Team • 04/21/2022
The vulnerability identified as CVE-2020-28634 represents a critical security flaw within the Computational Geometry Algorithms Library (CGAL) version 5.1.1, specifically within its Nef polygon-parsing functionality. This issue manifests through multiple code execution vulnerabilities that arise from improper handling of malformed input files during the parsing process of Nef polygons. The vulnerability affects the libcgal component of CGAL, which is widely used in computational geometry applications and CAD software where geometric operations and polygon manipulations are essential. The flaw exists in the SNC_io_parser::read_sedge() function located in the Nef_S2/SNC_io_parser.h file, making it particularly dangerous as it operates at a fundamental level of geometric data processing.
The technical implementation of this vulnerability involves an out-of-bounds read condition that occurs when parsing polygon edges within the Nef structure. The specific location of the issue is in the seh->next() operation within the read_sedge() function, where the parser attempts to access memory beyond the allocated bounds of the input data structure. This out-of-bounds read creates a type confusion scenario that can be exploited to manipulate memory layout and potentially execute arbitrary code. The vulnerability stems from insufficient input validation and boundary checking during the parsing of Nef polygon data, allowing attackers to craft specially formatted malicious files that trigger the memory access violations. This type of vulnerability aligns with CWE-125 (Out-of-Bounds Read) and CWE-787 (Out-of-bounds Write) classifications, representing a classic example of memory safety issues in C++ applications that handle complex geometric data structures.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it provides attackers with potential code execution capabilities that could be leveraged in various attack vectors. The vulnerability can be triggered through any application that utilizes CGAL's Nef polygon parsing functionality, including CAD software, geometric computation tools, and any system that processes polygonal data from untrusted sources. An attacker with the ability to provide malicious input files to a vulnerable application could potentially execute arbitrary code with the privileges of the affected process, leading to complete system compromise. This vulnerability particularly affects systems where geometric data is parsed from external sources without proper validation, making it relevant to industries such as automotive design, architectural software, and geographic information systems where CGAL is commonly deployed. The attack surface is broad due to the widespread use of CGAL in commercial and open-source applications, making this vulnerability particularly concerning from a security perspective.
Mitigation strategies for CVE-2020-28634 should prioritize immediate patching of affected CGAL installations to version 5.1.2 or later, which contains the necessary fixes for the out-of-bounds read and type confusion issues. Organizations should implement input validation measures that sanitize all polygon data before processing, particularly when dealing with external or untrusted inputs. The principle of least privilege should be enforced by running applications using minimal required permissions, reducing the potential impact of successful exploitation. Network segmentation and monitoring should be implemented to detect unusual file processing patterns that might indicate exploitation attempts. Additionally, developers should adopt defensive programming practices such as bounds checking, memory safety validations, and comprehensive error handling within their geometric computation modules. Security teams should monitor for any reports of exploitation attempts and maintain updated threat intelligence regarding similar vulnerabilities in related libraries. The ATT&CK framework categorizes this vulnerability under T1059 (Command and Scripting Interpreter) and T1203 (Exploitation for Client Execution) as exploitation techniques that could be leveraged to achieve code execution through memory corruption vulnerabilities.