CVE-2005-3625 in Linux
Summary
by MITRE
Xpdf, as used in products such as gpdf, kpdf, pdftohtml, poppler, teTeX, CUPS, libextractor, and others, allows attackers to cause a denial of service (infinite loop) via streams that end prematurely, as demonstrated using the (1) CCITTFaxDecode and (2) DCTDecode streams, aka "Infinite CPU spins."
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Analysis
by VulDB Data Team • 07/07/2021
The vulnerability described in CVE-2005-3625 represents a critical denial of service flaw affecting Xpdf library implementations across numerous PDF processing applications and systems. This vulnerability specifically targets the handling of malformed PDF streams within the CCITTFaxDecode and DCTDecode compression algorithms, which are fundamental components of PDF document rendering and processing. The affected software ecosystem includes popular tools such as gpdf, kpdf, pdftohtml, poppler, teTeX, CUPS, and libextractor, indicating the widespread impact of this flaw across different PDF handling mechanisms. The vulnerability stems from insufficient input validation and error handling within the stream processing logic of these compression algorithms.
The technical implementation of this vulnerability exploits the way Xpdf processes compressed data streams during PDF document parsing. When encountering streams that end prematurely, the CCITTFaxDecode and DCTDecode algorithms fail to properly validate stream boundaries and data integrity. This leads to the algorithms entering infinite loops during decompression operations, causing continuous CPU spinning where the processor remains occupied indefinitely without making progress. The flaw specifically manifests when the decompression routines do not properly detect end-of-stream conditions or when they fail to implement proper termination checks for compressed data sequences. The infinite loop behavior consumes excessive CPU resources and effectively renders the affected applications unavailable for legitimate use.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader system stability and resource management concerns. Attackers can exploit this vulnerability by crafting malicious PDF documents containing malformed streams that trigger the infinite loop behavior in any application utilizing the vulnerable Xpdf library. This creates a significant risk for systems processing untrusted PDF content, including web servers, email gateways, document management systems, and office automation platforms. The sustained CPU consumption can lead to system performance degradation, resource exhaustion, and potential system crashes in resource-constrained environments. Organizations relying on PDF processing for business-critical operations face substantial operational risks when this vulnerability remains unpatched.
The vulnerability aligns with CWE-835, which specifically addresses infinite loops in software implementations, and demonstrates characteristics consistent with ATT&CK technique T1499.004 for resource exhaustion attacks. The flaw represents a classic example of insufficient input validation where compressed data streams are not properly bounded or verified before processing. Effective mitigations include applying the latest security patches from software vendors, implementing input validation and stream boundary checking mechanisms, and deploying sandboxing or restricted execution environments for PDF processing. System administrators should also consider implementing rate limiting and resource monitoring to detect and prevent exploitation attempts. The vulnerability underscores the importance of robust error handling in compression algorithm implementations and highlights the need for comprehensive security testing of document processing libraries. Organizations should prioritize updating their PDF handling applications to versions containing fixes for this vulnerability, as the infinite loop behavior can be exploited to create sustained denial of service conditions that are difficult to detect and mitigate.