CVE-2018-4895 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. The vulnerability is caused by the computation that writes data past the end of the intended buffer; the computation is part of the image conversion engine when processing Enhanced Metafile Format Plus (EMF+) data. An attacker can potentially leverage the vulnerability to corrupt sensitive data or execute arbitrary code.
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Analysis
by VulDB Data Team • 02/10/2023
The vulnerability identified as CVE-2018-4895 represents a critical buffer overflow flaw within Adobe Acrobat Reader's image processing capabilities. This security weakness affects multiple versions of the software including 2018.009.20050 and earlier, 2017.011.30070 and earlier, and 2015.006.30394 and earlier versions. The flaw manifests specifically within the Enhanced Metafile Format Plus (EMF+) image conversion engine, which is responsible for processing vector graphics and metafile formats commonly used in document rendering. The buffer overflow occurs during the computation process where data is written beyond the boundaries of the intended memory buffer, creating a potential exploitation vector for malicious actors. This type of vulnerability falls under CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows data to overwrite adjacent memory locations.
The operational impact of this vulnerability extends beyond simple data corruption, presenting a significant risk for arbitrary code execution. When an attacker crafts malicious EMF+ data and embeds it within a PDF document, the vulnerable image conversion engine processes this data without adequate boundary verification. The overflow can overwrite critical memory segments including return addresses, function pointers, or other control data structures that govern program execution flow. This memory corruption can be leveraged to redirect program execution to attacker-controlled code, effectively enabling remote code execution capabilities. The vulnerability's exploitation potential aligns with ATT&CK technique T1203, which covers exploitation for execution through the manipulation of program execution flow. Security researchers have noted that the attack surface is particularly concerning because PDF documents are widely distributed and frequently opened, making this vulnerability an attractive target for phishing campaigns and targeted attacks.
The technical nature of this buffer overflow places it within the realm of memory safety vulnerabilities that have historically been exploited in numerous high-profile attacks. The flaw demonstrates a classic case of insufficient input validation where the EMF+ parser fails to properly verify the size and boundaries of incoming data before processing it. This type of vulnerability is particularly dangerous in document readers because these applications often process untrusted content from external sources without the same security restrictions applied to other software components. Organizations using affected versions of Adobe Acrobat Reader face significant risk exposure, as the vulnerability can be triggered simply by opening a maliciously crafted PDF file. The exploitation requires no user interaction beyond document opening, making it particularly stealthy and dangerous in enterprise environments where document sharing is common.
Mitigation strategies for CVE-2018-4895 should prioritize immediate patching of affected Adobe Acrobat Reader versions to the latest security updates provided by Adobe. Organizations should implement network-based protections including email filtering and web proxy controls to prevent the delivery of potentially malicious PDF files containing crafted EMF+ data. Security teams should also consider implementing application whitelisting policies that restrict the execution of Adobe Reader to trusted environments only. Additionally, regular security assessments should include verification of Adobe Reader installations to ensure all systems are updated with the latest security patches. The vulnerability highlights the importance of maintaining current software versions and implementing comprehensive patch management processes to protect against known security flaws. Organizations should also consider deploying sandboxing technologies for PDF processing and implementing multi-layered security controls to reduce the risk of exploitation through file format vulnerabilities.