CVE-2018-8101 in Xpdf
Summary
by MITRE
The JPXStream::inverseTransformLevel 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-2018-8101 represents a critical heap-based buffer over-read flaw within the JPXStream::inverseTransformLevel function of xpdf version 4.00. This issue specifically affects the JPXStream.cc source file and manifests when processing certain maliciously crafted pdf files. The vulnerability occurs during the execution of pdftohtml utility, which is commonly used for converting pdf documents into html format. The flaw stems from inadequate bounds checking within the inverse transform level processing routine, where the application fails to properly validate input data boundaries before performing memory operations. This allows an attacker to craft a specially formatted pdf file that, when processed by the vulnerable xpdf library, triggers unauthorized memory access patterns. The buffer over-read condition arises when the function attempts to read data beyond the allocated heap memory boundaries, resulting in unpredictable behavior and system instability.
The operational impact of this vulnerability extends beyond simple denial of service, as it can lead to complete application crashes and potentially provide a foothold for more sophisticated attacks. When exploited, the vulnerability causes the pdftohtml utility to terminate abruptly due to memory access violations, effectively rendering the tool unusable for legitimate document conversion tasks. The heap-based nature of the buffer over-read means that the memory corruption can potentially be leveraged to manipulate program execution flow, making this vulnerability particularly concerning for systems that rely on automated pdf processing. Security researchers have categorized this issue under CWE-125, which specifically addresses out-of-bounds read vulnerabilities in software applications. The vulnerability demonstrates characteristics consistent with attack patterns documented in the MITRE ATT&CK framework under the T1059.007 technique for command and scripting interpreter, as it can be exploited through crafted input files to achieve unauthorized system behavior.
Mitigation strategies for CVE-2018-8101 primarily focus on immediate software updates and input validation measures. The most effective remediation involves upgrading to xpdf version 4.01 or later, where the buffer over-read vulnerability has been addressed through proper bounds checking implementation. Organizations should also implement strict input sanitization protocols for pdf files processed through xpdf-based tools, including preliminary file validation and size limitations to prevent exploitation attempts. Additional defensive measures include deploying network segmentation to limit exposure of vulnerable systems, implementing application whitelisting policies to restrict execution of potentially vulnerable utilities, and establishing monitoring procedures to detect unusual application crash patterns. Security teams should also consider implementing sandboxing mechanisms when processing untrusted pdf documents, as this approach can contain the impact of any successful exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper memory management practices in security-sensitive applications and the necessity of regular security updates to protect against known exploits.