CVE-2020-21819 in LibreDWG
Summary
by MITRE • 05/18/2021
A heap based buffer overflow vulnerability exists in GNU LibreDWG 0.10.2641via htmlescape ../../programs/escape.c:51.
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Analysis
by VulDB Data Team • 05/22/2021
The heap-based buffer overflow vulnerability identified as CVE-2020-21819 resides within GNU LibreDWG version 0.10.2641, specifically in the htmlescape function located at ../../programs/escape.c line 51. This vulnerability represents a critical security flaw that can be exploited to compromise system integrity and potentially execute arbitrary code. The issue stems from improper input validation and memory management within the HTML escaping routine that processes data for web-based output generation. The vulnerability manifests when the application processes malformed or excessively long input strings that exceed the allocated heap buffer boundaries, creating conditions ripe for memory corruption and exploitation.
This heap overflow vulnerability operates under CWE-121, which categorizes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations. The flaw directly impacts the program's memory management system and can be leveraged by adversaries to manipulate program execution flow, potentially leading to complete system compromise. The vulnerability is particularly concerning because it occurs in a utility function designed for HTML escaping, suggesting that any application utilizing LibreDWG for processing user-supplied data could become vulnerable to this attack vector. Attackers could craft malicious input strings that, when processed through the htmlescape function, trigger the buffer overflow condition and enable code execution in the context of the running process.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can be exploited to achieve arbitrary code execution, privilege escalation, or denial of service conditions. When exploited successfully, the heap overflow allows attackers to overwrite critical memory structures, function pointers, or return addresses, potentially enabling remote code execution. The vulnerability affects systems that use GNU LibreDWG for processing AutoCAD drawing files or other DWG format data, particularly in web applications or services that convert these files to HTML format. The attack surface is broadened by the fact that this is a library-level vulnerability, meaning that any software components or applications that depend on LibreDWG for file processing could be indirectly affected.
Mitigation strategies for CVE-2020-21819 should prioritize immediate patching of the affected GNU LibreDWG version to the latest available release that contains the fix for the heap overflow condition. Organizations should implement input validation measures that enforce strict bounds checking on all data processed through the affected function, including length limitations and sanitization of user-supplied inputs. Network segmentation and access controls should be enforced to limit exposure of systems that utilize LibreDWG functionality, particularly in web-facing applications. Additionally, implementing heap protection mechanisms such as stack canaries, address space layout randomization, and data execution prevention can provide additional defense-in-depth measures. Regular security assessments and vulnerability scanning should be conducted to identify any other potentially affected components that might leverage the vulnerable library, while monitoring for exploitation attempts through intrusion detection systems that can detect anomalous memory access patterns or buffer overflow indicators. The vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1203 for Exploitation for Client Execution, demonstrating the potential for both code injection and client-side exploitation scenarios.