CVE-2018-4974 in Acrobat Reader
Summary
by MITRE
Adobe Acrobat and Reader versions 2018.011.20038 and earlier, 2017.011.30079 and earlier, and 2015.006.30417 and earlier have a Use-after-free vulnerability. Successful exploitation could lead to arbitrary code execution in the context of the current user.
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Analysis
by VulDB Data Team • 03/13/2023
Adobe Acrobat and Reader contain a critical use-after-free vulnerability in their handling of PDF files that affects multiple versions including 2018.011.20038 and earlier, 2017.011.30079 and earlier, and 2015.006.30417 and earlier. This vulnerability falls under the CWE-416 category of Use After Free, where a program continues to reference memory after it has been freed, creating a potential exploitation vector for attackers. The flaw occurs during the processing of malformed PDF objects that trigger improper memory management during the parsing of document elements. When a malicious PDF file is opened, the application's memory management routines fail to properly handle the deallocation of specific objects, leaving pointers that can be manipulated by an attacker to execute arbitrary code with the privileges of the current user. The vulnerability stems from insufficient bounds checking and memory management controls within the PDF parsing engine, particularly when processing embedded objects or complex data structures. Attackers can craft specially designed PDF documents that, when opened by an affected version of Adobe Reader or Acrobat, cause the application to free memory associated with certain objects while still maintaining references to them. This creates a scenario where subsequent memory operations can be redirected to execute malicious code, potentially allowing for complete system compromise. The exploitability of this vulnerability is enhanced by the fact that it requires no special privileges to trigger, making it particularly dangerous in targeted attacks where users might be tricked into opening malicious documents. The security implications extend beyond simple code execution, as successful exploitation could lead to privilege escalation, data theft, or the installation of additional malware. This vulnerability aligns with ATT&CK technique T1203 (Exploitation for Client Execution) and represents a significant risk to enterprise environments where users frequently open PDF documents from untrusted sources. Organizations should immediately apply patches from Adobe to mitigate this risk, as the vulnerability has been actively exploited in the wild. The use-after-free condition creates a window of opportunity for attackers to manipulate memory layouts and redirect execution flow, making it a preferred target for advanced persistent threat actors seeking to establish persistent access to compromised systems. This vulnerability demonstrates the critical importance of proper memory management in document processing applications and highlights the need for robust input validation and sanitization in software that handles complex file formats.
The technical exploitation of CVE-2018-4974 requires understanding the memory layout and object lifecycle management within Adobe's PDF processing libraries. When a PDF document is parsed, various objects such as dictionaries, arrays, and streams are created and eventually freed during garbage collection processes. The vulnerability occurs when these objects are freed prematurely while still being referenced by other components of the parsing engine, creating a dangling pointer that can be overwritten with attacker-controlled data. This type of vulnerability is particularly challenging to detect and exploit because it depends on precise timing and memory layout conditions that vary between different system configurations. The impact of exploitation extends beyond immediate code execution to include potential privilege escalation scenarios, as the compromised application typically runs with the privileges of the user who opened the document. This vulnerability represents a classic example of how complex software systems can introduce security flaws through seemingly simple memory management operations, and it underscores the importance of thorough security testing and code review processes for applications handling untrusted input data. Organizations should implement comprehensive security measures including email filtering, web application firewalls, and user education to reduce the risk of successful exploitation, while also maintaining up-to-date patch management processes to ensure timely remediation of such vulnerabilities. The vulnerability's classification under CWE-416 emphasizes the fundamental nature of the memory management flaw and its potential for widespread impact across different operating systems and deployment scenarios where Adobe Reader or Acrobat is installed.