CVE-2018-4885 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 Enhanced Metafile Format processing engine (within the image conversion module). A successful attack can lead to sensitive data exposure.
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Analysis
by VulDB Data Team • 07/23/2024
This vulnerability exists within Adobe Acrobat Reader's Enhanced Metafile Format processing engine, specifically within the image conversion module where buffer over-read conditions occur during the handling of malformed EMF files. The flaw manifests when the application processes Enhanced Metafile Format data structures that contain improperly calculated dimensions or data lengths, causing the processing engine to attempt reading memory locations beyond the allocated buffer boundaries. This type of vulnerability falls under the category of buffer over-read conditions that are classified as CWE-125 in the Common Weakness Enumeration framework, representing an out-of-bounds read where an application accesses memory beyond the bounds of a buffer.
The technical implementation of this vulnerability involves the processing of EMF file headers and data structures where the application fails to properly validate the length parameters of various metafile records before attempting to parse and convert them into displayable image formats. When encountering malformed EMF files with incorrect record lengths or corrupted data, the processing engine continues to read beyond the intended buffer limits, potentially accessing adjacent memory regions that may contain sensitive information such as credentials, session tokens, or other confidential data. This behavior represents a classic buffer over-read vulnerability that can be exploited through crafted malicious files delivered via social engineering or other attack vectors.
The operational impact of this vulnerability extends beyond simple data exposure, as it can potentially allow attackers to extract sensitive information from the application's memory space. Attackers who can successfully deliver a malicious EMF file to a victim running an affected version of Adobe Acrobat Reader could potentially access confidential data that resides in adjacent memory locations, including but not limited to user credentials, system information, or other application-specific data. This vulnerability affects multiple versions of Adobe Acrobat Reader across different release cycles, indicating a persistent issue in the image conversion module's handling of EMF format processing that has remained unaddressed for several years.
The attack surface for this vulnerability is particularly concerning given that Adobe Acrobat Reader is widely deployed across enterprise environments and is commonly used to open documents received via email or downloaded from untrusted sources. The vulnerability can be exploited through various delivery mechanisms including phishing emails containing malicious attachments, compromised websites, or malicious file sharing platforms. From an ATT&CK framework perspective, this vulnerability maps to techniques involving initial access through malicious files and privilege escalation through information disclosure, potentially enabling further attacks within the target environment. The lack of input validation in the EMF processing engine creates a persistent threat vector that remains exploitable as long as affected versions are in use.
Mitigation strategies for this vulnerability include immediate patching of affected Adobe Acrobat Reader installations to versions that contain the necessary security fixes for the EMF processing engine. Organizations should implement strict file validation policies that prevent the opening of untrusted EMF files or other potentially malicious formats through sandboxing techniques. Network-based security controls such as email filtering and web proxies can help prevent the delivery of malicious EMF files to end users. Additionally, regular security awareness training for users to recognize suspicious email attachments and download sources remains critical in reducing the risk of exploitation. System administrators should also consider implementing application whitelisting policies that restrict the execution of untrusted applications and file formats that may contain vulnerabilities like CVE-2018-4885.