CVE-2017-18184 in QPDF
Summary
by MITRE
An issue was discovered in QPDF before 7.0.0. There is a stack-based out-of-bounds read in the function iterate_rc4 in QPDF_encryption.cc.
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Analysis
by VulDB Data Team • 02/06/2023
The vulnerability identified as CVE-2017-18184 represents a critical stack-based out-of-bounds read flaw within the QPDF library version 6.0.4 and earlier. This issue resides in the iterate_rc4 function located within the QPDF_encryption.cc source file, making it a significant concern for any system utilizing QPDF for PDF processing operations. The flaw manifests when the library processes encrypted PDF documents, specifically during the decryption phase where RC4 encryption algorithms are employed.
The technical nature of this vulnerability stems from improper bounds checking within the iterate_rc4 function which handles the RC4 stream cipher operations during PDF decryption. When processing malformed or specially crafted PDF files, the function fails to validate array indices against buffer boundaries, allowing an attacker to read data from memory locations beyond the allocated stack space. This out-of-bounds read condition can potentially expose sensitive information stored in adjacent memory locations, including cryptographic keys, temporary variables, or other confidential data structures that may be present in the program's memory space.
From an operational perspective, this vulnerability poses substantial risks to systems that process untrusted PDF content, particularly those serving as document processing servers, email gateways, or content management systems. An attacker could exploit this weakness by crafting a malicious PDF file designed to trigger the out-of-bounds read condition, potentially leading to information disclosure or further exploitation attempts. The vulnerability aligns with CWE-125, which specifically addresses out-of-bounds read conditions, and can be categorized under ATT&CK technique T1059.007 for execution through PDF-based attacks. The impact extends beyond simple information disclosure, as the leaked memory contents might contain sensitive data that could aid in more sophisticated attacks against the target system.
The remediation strategy for this vulnerability requires immediate upgrading to QPDF version 7.0.0 or later, where the bounds checking has been properly implemented to prevent the out-of-bounds read condition. Organizations should also implement defensive measures such as validating PDF files through multiple layers of security checks, deploying sandboxed environments for PDF processing, and monitoring for suspicious PDF file patterns that might indicate exploitation attempts. Additionally, system administrators should consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts, while maintaining regular vulnerability assessments to identify and remediate similar issues within their software stack.