CVE-2020-35629 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_sloop() slh->facet().
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Analysis
by VulDB Data Team • 04/21/2022
The CVE-2020-35629 vulnerability represents a critical security flaw within the Computational Geometry Algorithms Library (CGAL) version 5.1.1, specifically within its Nef polygon-parsing functionality. This vulnerability exists in the libcgal component of CGAL, which is widely used for computational geometry operations in various software applications. The flaw manifests through multiple code execution pathways that stem from improper handling of malformed input data during polygon parsing operations. The vulnerability is particularly concerning because it can be exploited through seemingly innocuous polygon data files that have been crafted to contain malicious structures, making it a significant threat vector for applications that process user-provided geometric data.
The technical implementation of this vulnerability involves an out-of-bounds read condition combined with type confusion within the Nef_S2/SNC_io_parser.h file, specifically within the SNC_io_parser::read_sloop() function. The flaw occurs when processing the slh->facet() component of the parsing routine, where the software fails to properly validate input boundaries before accessing memory locations. This type confusion vulnerability arises from the improper handling of data structures that can be interpreted differently based on how the parser processes the input file. The out-of-bounds read allows an attacker to access memory regions beyond the intended data boundaries, potentially exposing sensitive information or enabling further exploitation techniques. The combination of these two vulnerabilities creates a particularly dangerous scenario where an attacker can manipulate memory layout to achieve arbitrary code execution.
The operational impact of CVE-2020-35629 extends beyond simple code execution, as it can be leveraged to compromise entire applications that rely on CGAL for geometric computations. Applications that process CAD files, geographic information systems, computer graphics rendering, or any software that handles polygonal data are at risk when using vulnerable versions of CGAL. The vulnerability can be triggered through various attack vectors including file uploads, network-based data processing, or any scenario where untrusted polygon data is parsed by affected software. The exploitation requires minimal privileges and can be automated, making it particularly dangerous in environments where applications process user-provided data without proper validation. This vulnerability directly maps to CWE-125 for out-of-bounds read and CWE-467 for use of sizeof() on a pointer, with potential ATT&CK techniques including T1059 for command and scripting interpreter and T1203 for Exploitation for Client Execution.
Mitigation strategies for CVE-2020-35629 require immediate action to upgrade to patched versions of CGAL, specifically version 5.1.2 or later where the vulnerabilities have been addressed through proper input validation and memory boundary checks. Organizations should implement comprehensive input sanitization measures for any polygon data processing within their applications, including strict validation of file formats and bounds checking. The fix involves adding proper boundary checks in the SNC_io_parser::read_sloop() function and ensuring that memory access patterns are validated before any data is read from potentially malicious input files. Additionally, implementing sandboxing techniques and privilege separation can help limit the potential impact of successful exploitation attempts. Security teams should also monitor for any indirect dependencies that might be using vulnerable versions of CGAL and ensure comprehensive patch management across all software components that may be affected by this vulnerability.