CVE-2018-7455 in Xpdf
Summary
by MITRE
An out-of-bounds read in JPXStream::readTilePart in JPXStream.cc in xpdf 4.00 allows attackers to launch denial of service via a specific pdf file, as demonstrated by pdftohtml.
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Analysis
by VulDB Data Team • 03/07/2025
CVE-2018-7455 represents a critical out-of-bounds read vulnerability within the JPXStream::readTilePart function of xpdf version 4.00. This flaw exists in the JPXStream.cc source file and specifically affects the handling of JPEG 2000 compressed data streams within PDF documents. The vulnerability arises when the pdftohtml utility processes maliciously crafted PDF files containing malformed JPEG 2000 data, leading to a buffer overread condition that can cause application crashes and denial of service attacks. The issue stems from insufficient bounds checking during the parsing of tile data structures within JPEG 2000 streams, where the code fails to validate array indices before accessing memory locations. This type of vulnerability maps directly to CWE-125, which describes out-of-bounds read conditions in software implementations. The operational impact of this vulnerability is significant as it allows remote attackers to craft PDF documents that trigger memory access violations when processed by xpdf-based applications, particularly affecting the pdftohtml conversion utility. Attackers can exploit this weakness by preparing specially crafted PDF files containing malformed JPEG 2000 data that causes the JPXStream parser to read beyond allocated memory boundaries, resulting in application instability and potential system crashes. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1203, where adversaries leverage software flaws to cause denial of service conditions. The flaw is particularly concerning because it operates at the parsing layer of PDF document processing, making it accessible through common document conversion workflows and potentially affecting any application that relies on xpdf's JPEG 2000 decompression capabilities. This vulnerability affects systems where xpdf 4.00 or earlier versions are installed, particularly those that process untrusted PDF content through the pdftohtml utility or similar tools. The root cause lies in inadequate input validation and memory management practices within the JPEG 2000 stream parser, where the code does not properly verify the integrity of tile data structures before attempting to access specific memory locations. The out-of-bounds read condition typically manifests as segmentation faults or memory access violations that terminate the application process, effectively providing a denial of service vector. Mitigation strategies should focus on upgrading to xpdf versions that contain patches addressing this specific buffer overread condition, implementing input validation measures, and employing sandboxing techniques when processing untrusted PDF documents. Organizations should also consider deploying network-based intrusion detection systems that can identify suspicious PDF file patterns and implementing strict access controls to limit exposure to potentially malicious document processing scenarios. The vulnerability underscores the importance of robust memory safety practices in multimedia parsing libraries and highlights the need for comprehensive testing of edge cases in compression format parsers.