CVE-2022-30524 in Xpdf
Summary
by MITRE • 05/09/2022
There is an invalid memory access in the TextLine class in TextOutputDev.cc in Xpdf 4.0.4 because the text extractor mishandles characters at large y coordinates. It can be triggered by (for example) sending a crafted pdf file to the pdftotext binary, which allows a remote attacker to cause a Denial of Service (Segmentation fault) or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 05/12/2022
The vulnerability identified as CVE-2022-30524 represents a critical memory access issue within the Xpdf library's text extraction functionality. This flaw exists in the TextLine class implementation within the TextOutputDev.cc source file of Xpdf version 4.0.4, where the text extraction engine fails to properly handle character positioning data at extremely high y-coordinate values. The vulnerability manifests when processing specially crafted pdf documents that contain text elements positioned at large y coordinates, creating an invalid memory access condition that can lead to system instability.
The technical root cause of this vulnerability stems from inadequate input validation and boundary checking within the text processing pipeline. When the pdftotext utility encounters pdf files containing characters positioned at unusually large y coordinates, the text extractor attempts to access memory locations beyond the allocated buffer boundaries or invalid memory regions. This improper handling of coordinate data violates fundamental memory safety principles and creates conditions where the application can attempt to read from or write to unauthorized memory locations, resulting in segmentation faults and potential system crashes.
The operational impact of CVE-2022-30524 extends beyond simple denial of service scenarios, as it represents a potential vector for more severe security consequences. Remote attackers can exploit this vulnerability by crafting malicious pdf documents that trigger the memory access violation when processed by any application utilizing the vulnerable Xpdf library. The vulnerability maps to CWE-125, which describes out-of-bounds read conditions, and aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation could potentially lead to arbitrary code execution depending on the specific memory corruption patterns. The vulnerability affects any system that relies on Xpdf's text extraction capabilities, including document processing servers, pdf conversion services, and applications that integrate pdf parsing functionality.
Mitigation strategies for CVE-2022-30524 require immediate patching of affected Xpdf installations to version 4.0.5 or later, which contains the necessary memory boundary checks and coordinate validation. Organizations should implement input sanitization measures for pdf processing workflows, including validation of coordinate data ranges and implementation of resource limits for text extraction operations. Additionally, deploying sandboxing techniques and restricting pdf processing to trusted sources can significantly reduce the risk of exploitation. System administrators should monitor for any unusual memory access patterns or segmentation fault occurrences in pdf processing services, as these could indicate attempted exploitation of the vulnerability. The fix addresses the underlying memory safety issue by implementing proper boundary checking and coordinate validation, preventing the invalid memory access condition that previously allowed attackers to cause system instability through crafted pdf content.