CVE-2020-20740 in PDFResurrect
Summary
by MITRE • 11/21/2020
PDFResurrect before 0.20 lack of header validation checks causes heap-buffer-overflow in pdf_get_version().
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Analysis
by VulDB Data Team • 12/09/2020
CVE-2020-20740 represents a heap buffer overflow vulnerability affecting PDFResurrect versions prior to 0.20, specifically within the pdf_get_version() function. This vulnerability stems from insufficient header validation checks during PDF file processing, creating a critical security gap that can be exploited by malicious actors. The flaw occurs when the application attempts to parse PDF headers without proper bounds checking, allowing an attacker to craft specially formatted PDF files that trigger memory corruption during version detection operations.
The technical implementation of this vulnerability involves the pdf_get_version() function failing to validate the length and structure of PDF file headers before attempting to read version information from memory. When processing malformed PDF files, the application reads beyond allocated heap buffers, causing unpredictable memory corruption that can lead to application crashes or potentially arbitrary code execution. This type of vulnerability falls under CWE-121, heap-based buffer overflow, and represents a classic example of insufficient input validation in security-critical applications. The vulnerability is particularly concerning because PDF processing applications often handle untrusted input from various sources, making them prime targets for exploitation.
The operational impact of CVE-2020-20740 extends beyond simple application instability to potential system compromise. Attackers can leverage this vulnerability through crafted PDF files delivered via email attachments, malicious websites, or compromised documents in document management systems. When exploited, the heap buffer overflow can cause denial of service conditions that may be used as a stepping stone for more sophisticated attacks. The vulnerability aligns with ATT&CK technique T1203, Exploitation for Client Execution, as it enables attackers to execute malicious code on victim systems through PDF processing applications. Additionally, this flaw demonstrates poor secure coding practices that violate industry standards for memory management and input validation.
Mitigation strategies for CVE-2020-20740 require immediate patching of PDFResurrect to version 0.20 or later, which includes proper header validation and bounds checking mechanisms. Organizations should implement defensive measures such as restricting PDF processing to trusted sources, deploying sandboxed environments for document analysis, and configuring network-level filtering to block suspicious PDF content. The vulnerability highlights the importance of input validation and memory safety practices that align with secure coding guidelines from organizations such as the Open Web Application Security Project. Regular security assessments of document processing applications and implementation of automated vulnerability scanning tools can help prevent similar issues in other software components. Network administrators should also consider implementing email filtering and web proxy solutions that can detect and block potentially malicious PDF files before they reach end-user systems.