CVE-2018-4893 in Acrobat Reader
Summary
by MITRE
An issue was discovered in Adobe Acrobat Reader 2018.009.20050 and earlier versions, 2017.011.30070 and earlier versions, 2015.006.30394 and earlier versions. This vulnerability occurs as a result of computation that reads data that is past the end of the target buffer; the computation is part of XPS font processing. A successful attack can lead to sensitive data exposure.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 02/10/2023
This vulnerability exists in Adobe Acrobat Reader across multiple version ranges including 2018.009.20050 and earlier, 2017.011.30070 and earlier, and 2015.006.30394 and earlier versions. The flaw manifests during XPS font processing when the application performs computations that read data beyond the boundaries of target buffers. This type of vulnerability falls under the category of buffer over-read conditions that are commonly classified as CWE-126 - Buffer Over-read within the Common Weakness Enumeration framework. The issue represents a critical security concern because it allows attackers to potentially access sensitive data that should remain protected within memory regions beyond the intended buffer boundaries.
The technical execution of this vulnerability occurs when Adobe Acrobat Reader processes XPS (XML Paper Specification) documents containing specially crafted font data. During the font processing routine, the application fails to properly validate buffer boundaries before performing memory reads, resulting in access to data that extends beyond the allocated memory space. This over-read behavior can expose confidential information such as memory contents, cryptographic keys, or other sensitive data that may be stored in adjacent memory locations. The vulnerability is particularly dangerous because it can be exploited through crafted XPS documents that users might encounter while opening legitimate PDF files or documents that contain embedded XPS content.
From an operational impact perspective, this vulnerability creates significant risks for organizations that rely on Adobe Acrobat Reader for document processing. Attackers can leverage this flaw by delivering malicious XPS content through various attack vectors including phishing emails, compromised websites, or malicious document attachments. When a user opens an infected document, the over-read condition triggers automatically, potentially exposing sensitive information that could be harvested by threat actors. The vulnerability operates at the memory access level, making it particularly stealthy as it may not produce obvious error messages or application crashes, thus allowing for prolonged exploitation without detection. This characteristic aligns with ATT&CK technique T1059.007 for Windows Command Shell and potentially T1566 for initial access through spearphishing.
Organizations should implement immediate mitigations including prompt application of Adobe's security patches and updates for Acrobat Reader across all affected versions. System administrators should consider implementing content filtering solutions that can identify and block suspicious XPS content before it reaches end users. Additionally, user education programs should emphasize the importance of only opening documents from trusted sources and avoiding unexpected attachments or links. Network security controls such as sandboxing mechanisms and deep packet inspection can help detect and prevent exploitation attempts. The vulnerability demonstrates the importance of proper input validation and boundary checking in document processing applications, particularly when handling complex formats like XPS that involve extensive font rendering operations. Regular security assessments and vulnerability scanning should include checks for outdated Acrobat Reader installations to ensure comprehensive protection against this and similar memory safety issues.