CVE-2020-28617 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->sfaces_last().
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Analysis
by VulDB Data Team • 04/18/2022
The vulnerability described represents a critical security flaw within the Computational Geometry Algorithms Library (CGAL) version 5.1.1, specifically affecting its polygon-parsing functionality used in Nef operations. This issue stems from inadequate input validation and memory management within the SNC_io_parser class, creating multiple attack vectors that could be exploited by malicious actors to achieve remote code execution. The vulnerability is particularly concerning because it affects the core geometric processing capabilities of CGAL, which is widely used in applications requiring robust computational geometry operations such as CAD software, geographic information systems, and scientific computing platforms.
The technical implementation of this vulnerability involves a combination of out-of-bounds read conditions and type confusion errors that occur during the parsing of malformed Nef polygon data structures. The specific flaw manifests in the SNC_io_parser::read_vertex() method within the Nef_S2/SNC_io_parser.h file where the vh->sfaces_last() operation accesses memory beyond allocated boundaries. This out-of-bounds read creates a type confusion scenario that can be leveraged by attackers to manipulate memory layout and potentially execute arbitrary code. The vulnerability demonstrates characteristics consistent with CWE-125 (Out-of-bounds Read) and CWE-476 (NULL Pointer Dereference), while also exhibiting behaviors aligned with ATT&CK technique T1059.007 (Command and Scripting Interpreter: JavaScript) through potential code execution pathways.
The operational impact of this vulnerability extends far beyond simple data corruption, as it can enable full system compromise when exploited. Attackers capable of crafting malicious Nef polygon files could trigger these vulnerabilities in applications that utilize CGAL for geometric processing, potentially leading to unauthorized code execution with the privileges of the affected application. This risk is particularly elevated in environments where CGAL is used in server-side applications or security-critical systems where input validation may be insufficient. The vulnerability affects not only direct users of CGAL but also downstream applications that depend on CGAL's geometric processing capabilities, creating a wide attack surface.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected CGAL versions to 5.1.2 or later, which contains the necessary fixes for the out-of-bounds read and type confusion issues. Organizations should implement strict input validation measures when processing Nef polygon data, including size limiting, format checking, and sanitization routines before any parsing operations. Additionally, runtime protections such as address space layout randomization (ASLR), stack canaries, and heap metadata protection should be enabled to make exploitation more difficult. Security monitoring should focus on detecting unusual file processing patterns or memory access violations that could indicate exploitation attempts, while also implementing network segmentation to limit potential lateral movement if compromise occurs.
The vulnerability landscape for CGAL highlights the importance of secure coding practices in mathematical and geometric libraries where memory safety is paramount. This issue demonstrates how seemingly benign parsing operations can become attack vectors when proper bounds checking and memory management are not implemented. The complexity of geometric algorithms combined with insufficient input validation creates opportunities for sophisticated exploits that can bypass traditional security measures, making regular security audits and vulnerability assessments crucial for maintaining system integrity in environments utilizing computational geometry libraries.