CVE-2024-4568 in Xpdf
Summary
by MITRE • 05/06/2024
In Xpdf 4.05 (and earlier), a PDF object loop in the PDF resources leads to infinite recursion and a stack overflow.
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Analysis
by VulDB Data Team • 12/05/2025
The vulnerability identified as CVE-2024-4568 affects Xpdf version 4.05 and earlier, representing a critical stack overflow condition that arises from improper handling of PDF object loops within resource structures. This flaw manifests when the PDF parser encounters circular references in object definitions, creating an infinite recursion scenario that eventually exhausts the available stack memory. The issue stems from the parser's inability to detect and terminate recursive object references, allowing maliciously crafted PDF documents to trigger denial of service conditions through excessive memory consumption.
This vulnerability directly maps to CWE-674, which describes "Uncontrolled Recursion" in software systems, and aligns with ATT&CK technique T1499.004 for "Endpoint Denial of Service" through resource exhaustion. The technical flaw occurs at the parsing layer where the PDF object resolution mechanism lacks proper termination conditions for circular references, causing the recursive descent parser to continuously invoke itself without reaching a base case. The stack overflow vulnerability represents a classic example of insufficient input validation and lacks proper recursion depth monitoring.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially be exploited in automated attack scenarios where adversaries craft PDF documents specifically designed to trigger the recursive loop. When exploited, the vulnerability results in application crashes, system instability, and can serve as a vector for more sophisticated attacks if combined with other vulnerabilities. The vulnerability affects any system that processes PDF files using the affected Xpdf library, including web applications, document viewers, and content management systems that utilize this parsing library for PDF handling.
Mitigation strategies should focus on immediate patching of the Xpdf library to version 4.06 or later, which includes proper recursion depth limiting and circular reference detection. Organizations should implement input validation measures that sanitize PDF content before processing, particularly in web-facing applications where PDF documents may be uploaded by untrusted users. Additional defensive measures include deploying sandboxing mechanisms for PDF processing, implementing memory limits for parsing operations, and establishing monitoring for unusual memory consumption patterns. Network segmentation and application whitelisting can further reduce the attack surface by limiting access to vulnerable PDF processing components. The fix addresses the root cause by introducing maximum recursion depth limits and circular reference detection algorithms that prevent the parser from entering infinite loops while maintaining proper PDF document parsing functionality.