CVE-2017-16389 in Acrobat Reader
Summary
by MITRE
An issue was discovered in Adobe Acrobat and Reader: 2017.012.20098 and earlier versions, 2017.011.30066 and earlier versions, 2015.006.30355 and earlier versions, and 11.0.22 and earlier versions. This vulnerability is an instance of a use after free vulnerability in the JavaScript engine. The mismatch between an old and a new object can provide an attacker with unintended memory access. Successful exploitation could lead to arbitrary code execution.
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Analysis
by VulDB Data Team • 01/24/2021
The vulnerability identified as CVE-2017-16389 represents a critical use after free flaw within Adobe Acrobat and Reader applications across multiple version ranges including 2017.012.20098 and earlier, 2017.011.30066 and earlier, 2015.006.30355 and earlier, and 11.0.22 and earlier versions. This type of vulnerability occurs when a program continues to reference memory that has already been freed, creating a dangerous condition where malicious actors can manipulate the memory state to execute arbitrary code. The issue resides within the JavaScript engine component of these applications, which processes user-supplied JavaScript code within PDF documents. The root cause stems from improper memory management where the application fails to properly track object references during JavaScript execution, leading to situations where freed memory locations become accessible to attackers. This specific vulnerability aligns with CWE-416, which defines use after free conditions as a class of memory safety issues that occur when a program continues to use a pointer after the memory it points to has been freed. The operational impact of this vulnerability is severe as it allows remote code execution without user interaction, making it particularly dangerous in targeted attack scenarios. Attackers can craft malicious PDF documents containing specially crafted JavaScript code that triggers the use after free condition when the document is opened, potentially leading to full system compromise. The exploitability of this vulnerability is enhanced by the fact that it requires no user interaction beyond opening the malicious document, making it particularly effective in phishing campaigns and targeted attacks. This weakness enables adversaries to leverage the ATT&CK technique T1059.007 for JavaScript execution and can facilitate broader compromise through subsequent attack vectors.
The technical nature of this use after free vulnerability stems from the JavaScript engine's inability to properly manage object lifecycles during dynamic code execution. When JavaScript objects are created and subsequently freed during normal operation, the memory management system should ensure that no further references to these objects remain. However, in the affected Adobe products, there exists a race condition or logic flaw where references to freed objects persist, allowing attackers to manipulate the freed memory location to inject and execute malicious code. This memory corruption vulnerability specifically affects the application's ability to properly handle JavaScript objects during garbage collection processes, creating a window where attackers can control what data resides in previously freed memory segments. The mismatch between old and new object states creates opportunities for attackers to predict memory layout patterns and overwrite critical data structures or function pointers, ultimately leading to code execution. The vulnerability's severity is compounded by the fact that it operates within the context of PDF document processing, where users frequently encounter and open documents from untrusted sources, making exploitation highly probable in real-world scenarios.
Organizations and individuals using affected Adobe Acrobat and Reader versions face significant risk from this vulnerability, particularly in environments where PDF documents are frequently exchanged and opened. The remote code execution capability means that attackers can compromise systems simply by delivering a malicious PDF file through email, web downloads, or other distribution methods. This vulnerability is especially concerning in enterprise environments where Adobe Reader is widely deployed and users regularly open PDF documents from external sources without proper security screening. The exploitation process typically involves crafting a PDF document containing malicious JavaScript code that triggers the use after free condition when parsed by the vulnerable application. Once successfully exploited, attackers can gain full control over the affected system, potentially leading to data theft, system compromise, or further lateral movement within the network. The vulnerability's persistence across multiple product versions indicates a fundamental flaw in the JavaScript engine implementation that required comprehensive patching across all affected releases. Security professionals should note that this vulnerability demonstrates the importance of proper memory management practices and the potential for seemingly benign scripting functionality to create critical security risks.
Mitigation strategies for CVE-2017-16389 primarily involve immediate patching of all affected Adobe Acrobat and Reader installations to the latest available versions that contain fixes for the use after free vulnerability. Organizations should implement strict document access controls, including disabling JavaScript execution in PDF readers where possible, and deploying sandboxing mechanisms to limit the potential impact of exploitation attempts. Network security measures such as PDF content filtering and deep packet inspection should be employed to detect and block potentially malicious PDF files before they reach end users. Regular security awareness training should emphasize the dangers of opening PDF documents from untrusted sources, as social engineering remains a primary attack vector for this vulnerability. System administrators should monitor for indicators of compromise including unusual network connections or process behavior that may suggest exploitation attempts. Additionally, implementing application whitelisting policies to restrict execution of untrusted PDF processing applications can provide an additional layer of protection. The vulnerability's classification under CWE-416 and its potential exploitation through ATT&CK techniques T1059.007 highlights the need for comprehensive security measures that address both the immediate patching requirements and broader defensive strategies. Organizations should also consider implementing endpoint detection and response solutions that can identify anomalous behavior indicative of memory corruption exploits. Regular vulnerability assessments and penetration testing should be conducted to ensure that all systems remain protected against similar memory safety issues that could potentially be exploited in the future.