CVE-2018-4896 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 the image conversion module that handles Enhanced Metafile Format Plus (EMF+) data. A successful attack can lead to sensitive data exposure.
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Analysis
by VulDB Data Team • 02/10/2023
This vulnerability in Adobe Acrobat Reader represents a classic buffer over-read condition that occurs within the image conversion module handling Enhanced Metafile Format Plus (EMF+) data. The flaw manifests when the software processes EMF+ formatted images, which are commonly used for vector graphics in Windows environments. The vulnerability is particularly concerning because it allows an attacker to manipulate the buffer boundary calculations during image processing, causing the application to read memory locations beyond the intended buffer limits. This type of vulnerability falls under the CWE-125 weakness category, which specifically addresses out-of-bounds read conditions that can lead to information disclosure and potentially more severe exploitation vectors.
The technical implementation of this vulnerability involves the image conversion module's handling of EMF+ data structures where boundary checks are insufficient or incorrectly implemented. When processing malformed EMF+ files, the software performs calculations that determine buffer sizes and memory access ranges without proper validation of input data boundaries. This allows an attacker to craft specially formatted EMF+ files that trigger the over-read condition, potentially exposing sensitive memory contents including stack data, heap data, or other process memory segments that may contain credentials, encryption keys, or other confidential information. The vulnerability is particularly dangerous in environments where users may encounter untrusted EMF+ content through email attachments, web downloads, or other attack vectors.
The operational impact of CVE-2018-4896 extends beyond simple information disclosure, as the over-read condition can potentially expose sensitive data that could be leveraged for further attacks. Attackers could exploit this vulnerability to extract memory contents that might include session tokens, user credentials, or application-specific data that could be used for privilege escalation or lateral movement within a network. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as it could enable an attacker to gain access to sensitive information that might be used to execute additional malicious payloads. The vulnerability affects multiple versions of Adobe Acrobat Reader, indicating a persistent flaw in the image processing module that was not adequately addressed through previous security updates.
Organizations should prioritize immediate remediation by updating to Adobe Acrobat Reader versions that have patched this vulnerability, specifically versions 2018.009.20051 or later. System administrators should implement network-based controls to block or scan EMF+ files, particularly when they originate from untrusted sources. The vulnerability demonstrates the importance of proper input validation and boundary checking in image processing libraries, as highlighted in industry security frameworks such as the OWASP Top Ten and NIST Cybersecurity Framework. Security teams should monitor for exploitation attempts through network traffic analysis, looking for unusual patterns in EMF+ file processing or memory access anomalies that might indicate exploitation of this vulnerability. Additionally, user education regarding the risks of opening untrusted attachments and files from unknown sources remains crucial in mitigating the overall attack surface for this type of vulnerability.