CVE-2005-0064 in kpdf
Summary
by MITRE
Buffer overflow in the Decrypt::makeFileKey2 function in Decrypt.cc for xpdf 3.00 and earlier allows remote attackers to execute arbitrary code via a PDF file with a large /Encrypt /Length keyLength value.
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Analysis
by VulDB Data Team • 07/01/2019
The vulnerability identified as CVE-2005-0064 represents a critical buffer overflow flaw within the xpdf PDF rendering library version 3.00 and earlier. This issue resides in the Decrypt::makeFileKey2 function located in the Decrypt.cc source file, which handles the decryption process for PDF files containing encrypted content. The flaw manifests when processing PDF documents that contain an excessively large /Encrypt /Length keyLength value, creating a condition where attacker-controlled input can overflow fixed-size buffers in memory.
The technical implementation of this vulnerability exploits the lack of proper input validation within the decryption routine. When xpdf processes a PDF file with an oversized encryption key length parameter, the Decrypt::makeFileKey2 function fails to validate the size of the keyLength value against the allocated buffer space. This allows malicious actors to craft PDF documents containing malformed encryption parameters that exceed the intended buffer boundaries, leading to memory corruption that can be leveraged for arbitrary code execution. The vulnerability operates at the application level within the PDF parsing and decryption subsystem, making it particularly dangerous as it can be triggered simply by opening a malicious PDF file.
The operational impact of this vulnerability extends beyond simple code execution to encompass full system compromise when exploited. Attackers can leverage this buffer overflow to inject and execute malicious code within the context of the xpdf application, potentially leading to complete system takeover if the application runs with elevated privileges. The vulnerability affects any system running xpdf versions 3.00 or earlier, including various Linux distributions, Unix systems, and Windows platforms where xpdf is installed. The remote exploitation capability means that attackers do not need physical access to the target system, as the vulnerability can be triggered through web browsers, email clients, or any application that utilizes the vulnerable xpdf library for PDF processing.
This vulnerability maps directly to CWE-121, which describes heap-based buffer overflow conditions, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation would likely involve executing malicious commands through the compromised application. The flaw demonstrates poor input validation practices and inadequate memory management within the cryptographic components of the PDF processing library. Organizations using vulnerable versions of xpdf should immediately implement mitigations including updating to patched versions, implementing network-based restrictions on PDF file handling, and deploying intrusion detection systems to monitor for exploitation attempts. The vulnerability also highlights the importance of proper bounds checking in cryptographic implementations and the need for robust input sanitization in security-critical applications processing untrusted data.
The exploitation of CVE-2005-0064 underscores the broader security implications of buffer overflow vulnerabilities in widely-used open source libraries. Given that xpdf was commonly integrated into numerous applications and web browsers, the potential attack surface was extensive, making this vulnerability particularly dangerous for organizations with legacy systems or those unable to immediately patch their software. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security patches and implementing defense-in-depth strategies to protect against such fundamental flaws in software implementations.