CVE-2018-8106 in Xpdf
Summary
by MITRE
The JPXStream::readTilePartData function in JPXStream.cc in xpdf 4.00 allows attackers to launch denial of service (heap-based buffer over-read and application crash) via a specific pdf file, as demonstrated by pdftohtml.
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Analysis
by VulDB Data Team • 03/07/2025
The vulnerability identified as CVE-2018-8106 resides within the JPXStream::readTilePartData function in the JPXStream.cc file of xpdf version 4.00. This flaw represents a heap-based buffer over-read condition that can be exploited to cause denial of service attacks, specifically targeting applications that process pdf files through the pdftohtml utility. The vulnerability manifests when processing specially crafted pdf files that contain malformed JPEG2000 data streams, creating a scenario where the application attempts to read beyond the allocated heap memory boundaries.
The technical implementation of this vulnerability stems from inadequate input validation within the JPXStream class, which handles JPEG2000 compressed data streams within pdf documents. When the readTilePartData function processes tile data from a malformed jpeg2000 stream, it fails to properly bounds-check array accesses or validate the size parameters of the data being read. This allows an attacker to craft a pdf file with maliciously structured jpeg2000 components that cause the function to attempt reading memory locations beyond the allocated buffer space, resulting in undefined behavior and subsequent application crashes.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged by attackers to disrupt legitimate pdf processing workflows in environments where automated pdf conversion tools are employed. Systems that rely on pdftohtml for document conversion, web applications processing user-uploaded pdf files, or document management platforms may become vulnerable to service disruption when encountering maliciously crafted pdf documents. The vulnerability is particularly concerning in server environments where pdf processing is automated and user input is not properly sanitized, as it could enable attackers to repeatedly crash services or consume excessive system resources.
This vulnerability aligns with CWE-125, which describes out-of-bounds read conditions in software systems, and demonstrates characteristics consistent with ATT&CK technique T1499.004, specifically application or system exploitation for denial of service. The flaw represents a classic heap memory corruption issue that can be exploited through crafted input data, making it particularly dangerous in environments where pdf processing is automated or where users can upload arbitrary pdf files to systems. Organizations should prioritize patching this vulnerability as it represents a readily exploitable condition that can lead to significant service disruption and potential business impact.
Mitigation strategies should include immediate deployment of patched versions of xpdf that address the buffer over-read condition in JPXStream.cc, along with implementing proper input validation and sanitization for pdf processing workflows. Additional protective measures include deploying web application firewalls that can detect and block malicious pdf files, implementing sandboxing for pdf processing operations, and establishing robust input validation at multiple layers of the processing pipeline. Organizations should also consider monitoring for unusual patterns of pdf processing failures that might indicate exploitation attempts, as well as maintaining up-to-date threat intelligence regarding similar vulnerabilities in pdf processing libraries.