CVE-2018-16368 in Xpdf
Summary
by MITRE
SplashXPath::strokeAdjust in splash/SplashXPath.cc in Xpdf 4.00 allows remote attackers to cause a denial of service (heap-based buffer over-read) via a crafted pdf file, as demonstrated by pdftoppm.
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Analysis
by VulDB Data Team • 03/07/2025
CVE-2018-16368 represents a heap-based buffer over-read vulnerability located within the SplashXPath::strokeAdjust function in the splash/SplashXPath.cc file of Xpdf version 4.00. This flaw exists within the graphics rendering component of the PDF processing library, specifically affecting how the software handles stroke adjustments during vector path rendering operations. The vulnerability manifests when processing maliciously crafted PDF files that contain specially constructed path data which triggers an improper bounds check during memory access operations. The issue occurs during the conversion process when pdftoppm utility attempts to render PDF pages containing problematic vector graphics, leading to unauthorized memory access beyond allocated buffer boundaries.
The technical exploitation of this vulnerability involves a remote attacker who can craft a PDF document containing malformed stroke adjustment parameters that cause the SplashXPath::strokeAdjust function to read memory locations beyond the intended buffer limits. This over-read condition occurs because the code fails to properly validate input parameters before performing memory operations, creating a scenario where the program attempts to access heap memory that has not been allocated for the current operation. The vulnerability is classified under CWE-125 as an out-of-bounds read, which falls within the broader category of memory safety issues that can lead to system instability and potential information disclosure. The flaw demonstrates characteristics consistent with the attack pattern described in the MITRE ATT&CK framework under technique T1059 for execution of malicious code through document processing.
The operational impact of CVE-2018-16368 extends beyond simple denial of service, as the heap-based buffer over-read can potentially lead to system crashes, application instability, and in some scenarios might provide a pathway for more sophisticated attacks. When exploited, this vulnerability allows an attacker to cause the pdftoppm utility to terminate unexpectedly or behave unpredictably, effectively preventing legitimate PDF processing operations from completing successfully. The vulnerability affects any system that utilizes Xpdf 4.00 for PDF rendering or conversion, including servers processing PDF documents, desktop applications, and automated workflows that depend on the library's graphics rendering capabilities. The remote nature of the attack means that simply opening or processing a malicious PDF file can trigger the vulnerability, making it particularly dangerous in environments where users might encounter untrusted PDF content.
Mitigation strategies for CVE-2018-16368 primarily focus on immediate software updates and version control measures to address the root cause of the vulnerability. Organizations should upgrade to Xpdf versions that contain the patched SplashXPath::strokeAdjust function, which implements proper bounds checking and input validation to prevent the buffer over-read condition. Additionally, system administrators should implement defensive measures such as restricting PDF processing to trusted sources, deploying sandboxed environments for PDF rendering operations, and configuring network firewalls to limit access to PDF processing services. The vulnerability highlights the importance of input validation and memory safety practices in PDF processing libraries, aligning with security best practices outlined in the OWASP Top Ten and other industry security frameworks. Regular security assessments and vulnerability scanning should be conducted to identify similar memory safety issues in other PDF processing components and ensure comprehensive protection against similar attack vectors.