CVE-2016-6939 in Acrobat Reader
Summary
by MITRE
Heap-based buffer overflow in Adobe Reader and Acrobat before 11.0.18, Acrobat and Acrobat Reader DC Classic before 15.006.30243, and Acrobat and Acrobat Reader DC Continuous before 15.020.20039 on Windows and OS X allows attackers to execute arbitrary code via unspecified vectors, a different vulnerability than CVE-2016-6994.
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Analysis
by VulDB Data Team • 09/23/2022
The heap-based buffer overflow vulnerability identified as CVE-2016-6939 represents a critical security flaw affecting Adobe Reader and Acrobat software across multiple versions and operating systems. This vulnerability exists within the heap memory management system of Adobe's document processing applications, specifically impacting versions prior to 11.0.18 for traditional Acrobat and Reader installations, as well as various DC Classic and Continuous versions. The flaw enables remote attackers to potentially execute arbitrary code on affected systems through unspecified attack vectors that differ from the related CVE-2016-6994 vulnerability, highlighting the complexity of Adobe's security landscape during this period.
The technical implementation of this heap-based buffer overflow occurs when the affected Adobe applications process maliciously crafted PDF files containing specially constructed data structures. During normal operation, these applications allocate memory on the heap to store temporary data and processing information. However, when encountering malformed input data, the memory allocation routines fail to properly validate input boundaries, allowing attackers to write data beyond the allocated heap buffer space. This overflow condition can overwrite adjacent memory locations, potentially corrupting program execution flow and enabling attackers to inject and execute malicious code with the privileges of the affected application.
The operational impact of CVE-2016-6939 extends significantly beyond simple code execution capabilities, as it provides attackers with a potential pathway to achieve full system compromise. When successfully exploited, this vulnerability allows adversaries to bypass standard security controls and execute arbitrary commands on target systems, potentially leading to data theft, system infiltration, or deployment of additional malware. The vulnerability's presence in both Windows and OS X environments demonstrates its cross-platform nature and the widespread potential for exploitation across different operating system families. Security researchers have classified this vulnerability under CWE-121, heap-based buffer overflow, which specifically addresses buffer overflows occurring in heap memory regions, making it particularly dangerous due to the unpredictable nature of heap memory corruption.
Attackers typically leverage this vulnerability through social engineering campaigns targeting end users, often delivering malicious PDF files through email attachments, compromised websites, or infected download sources. The exploitation process requires minimal user interaction, as simply opening a malicious document within the vulnerable Adobe application can trigger the buffer overflow condition. This makes the vulnerability particularly dangerous in enterprise environments where users frequently open documents from external sources. The ATT&CK framework categorizes this type of vulnerability exploitation under the T1203 - Exploitation for Client Execution technique, where adversaries leverage software vulnerabilities to execute malicious code on targeted systems.
Organizations affected by CVE-2016-6939 should immediately implement comprehensive mitigation strategies including mandatory software updates to the latest Adobe Reader and Acrobat versions, deployment of network-based intrusion detection systems to monitor for exploitation attempts, and implementation of email filtering solutions to prevent delivery of malicious PDF attachments. Security teams should also consider deploying application whitelisting policies to restrict execution of unauthorized Adobe software versions and conduct regular vulnerability assessments to identify any remaining unpatched systems. The vulnerability's classification as a heap-based buffer overflow underscores the importance of memory safety practices and proper input validation in software development, particularly for applications handling untrusted data sources such as PDF documents.