CVE-2018-4900 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 JavaScript manipulation of an Annotation object. A successful attack can lead to sensitive data exposure.
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Analysis
by VulDB Data Team • 02/10/2023
The vulnerability identified as CVE-2018-4900 represents a critical buffer over-read flaw in Adobe Acrobat Reader affecting multiple version ranges including 2018.009.20050 and earlier, 2017.011.30070 and earlier, and 2015.006.30394 and earlier versions. This issue manifests specifically within the JavaScript processing engine when handling Annotation objects, creating a scenario where the application attempts to read memory locations beyond the allocated buffer boundaries. The flaw stems from inadequate bounds checking during the manipulation of annotation data structures, allowing malicious actors to potentially access sensitive information stored in adjacent memory regions. Such buffer over-read conditions are classified under CWE-125 as "Out-of-bounds Read" and represent a common class of memory safety vulnerabilities that can lead to information disclosure or potential exploitation for more severe attacks. The vulnerability is particularly concerning in the context of PDF document processing where JavaScript execution is commonly enabled, making it a prime target for attackers seeking to extract confidential data from memory.
The technical implementation of this vulnerability occurs when Adobe Acrobat Reader processes JavaScript code embedded within PDF documents that manipulate Annotation objects. During the execution of such JavaScript, the application performs calculations that determine memory offsets for reading annotation data, but fails to properly validate whether these calculated offsets remain within the legitimate buffer boundaries. When an attacker crafts a malicious PDF document containing specially constructed annotation data, the JavaScript engine executes code that causes the application to read beyond the intended buffer limits, potentially exposing sensitive information from adjacent memory locations. This type of vulnerability falls under the ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript" and represents a memory corruption vulnerability that can be leveraged for information disclosure. The flaw is particularly dangerous because it occurs during normal document processing operations, meaning users can be exploited simply by opening a malicious document without any additional interaction required from the victim.
The operational impact of CVE-2018-4900 extends beyond simple information disclosure to potentially enable more sophisticated attacks within the context of a compromised system. When an attacker successfully exploits this vulnerability, they can access sensitive data that may include encryption keys, user credentials, system information, or other confidential data stored in memory adjacent to the vulnerable buffer. This information exposure can facilitate further attacks including privilege escalation, lateral movement, or the creation of more targeted exploits against the compromised system. The vulnerability affects a widely used application with extensive deployment across enterprise environments, making the potential impact significant for organizations that rely on Adobe Acrobat Reader for document processing. Organizations running affected versions of Adobe Acrobat Reader are particularly vulnerable since the exploit can be delivered through email attachments, web downloads, or other common attack vectors that do not require user interaction beyond opening a malicious PDF document. The vulnerability's persistence across multiple major versions indicates a fundamental flaw in the application's memory management and bounds checking mechanisms, requiring immediate remediation through official patches provided by Adobe.
Mitigation strategies for CVE-2018-4900 should prioritize immediate patching of affected Adobe Acrobat Reader installations to the latest available versions that contain the necessary security fixes. Organizations should implement strict document validation policies that prevent execution of JavaScript code within PDF documents when possible, particularly in environments where users may encounter untrusted documents. Network-level defenses including web proxies and email security appliances should be configured to scan and block potentially malicious PDF files before they reach end users. Additionally, security teams should monitor for indicators of compromise related to this vulnerability and implement application whitelisting policies to restrict execution of untrusted PDF processing applications. The vulnerability highlights the importance of maintaining up-to-date security patches for widely deployed applications and demonstrates the critical need for regular security assessments of commonly used software packages. Organizations should also consider implementing sandboxing techniques for PDF document processing to limit the potential impact of successful exploitation attempts. Regular security training for users on identifying and avoiding suspicious email attachments and web downloads remains essential in defending against exploitation of this class of vulnerability.