CVE-2017-2950 in Acrobat Reader
Summary
by MITRE
Adobe Acrobat Reader versions 15.020.20042 and earlier, 15.006.30244 and earlier, 11.0.18 and earlier have an exploitable use after free vulnerability in the XFA engine, related to layout functionality. Successful exploitation could lead to arbitrary code execution.
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Analysis
by VulDB Data Team • 10/28/2022
The vulnerability identified as CVE-2017-2950 represents a critical use after free flaw within Adobe Acrobat Reader's XFA engine, specifically impacting versions through 15.020.20042, 15.006.30244, and 11.0.18. This issue resides in the application's handling of layout functionality within the XFA (XML Forms Architecture) processing subsystem, which is responsible for rendering complex forms and documents. The flaw manifests when the software improperly manages memory allocation and deallocation processes, creating conditions where freed memory locations can be accessed and reused by malicious code. Such vulnerabilities are particularly dangerous because they often allow attackers to execute arbitrary code with the privileges of the targeted user, making them prime targets for exploitation in targeted attacks.
The technical nature of this vulnerability places it squarely within the CWE-416 category of use after free conditions, where memory that has been freed is accessed again, potentially leading to memory corruption and code execution. The XFA engine's layout functionality creates complex memory structures that, when improperly handled, can result in attackers manipulating freed memory blocks to redirect execution flow. This vulnerability exploits the fundamental memory management mechanisms within Adobe's document processing pipeline, where the application fails to properly validate memory references after objects have been deallocated. The attack surface is particularly wide given that Acrobat Reader is widely deployed across enterprise environments and is frequently used to open PDF documents from untrusted sources, making it a high-value target for threat actors seeking persistent access to systems.
The operational impact of CVE-2017-2950 extends beyond simple code execution, as it can be leveraged for complete system compromise when combined with other attack vectors. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation typically enables attackers to execute malicious payloads that can establish persistence, exfiltrate data, or escalate privileges within the compromised environment. Organizations running affected versions of Adobe Acrobat Reader face significant risk, as the vulnerability can be triggered through simple PDF document opening, requiring no additional user interaction beyond viewing the malicious content. The attack chain often involves social engineering to deliver the malicious PDF, but once opened, the exploit can automatically execute code without user intervention, making it particularly effective in phishing campaigns and targeted attacks against high-value targets.
Mitigation strategies for this vulnerability require immediate patching of all affected Adobe Acrobat Reader installations, with particular attention to versions prior to the security updates released by Adobe. System administrators should implement strict document handling policies that limit PDF file execution and require verification of document sources before opening. Network-based defenses should include PDF content filtering and sandboxing mechanisms to isolate potentially malicious documents. The vulnerability also highlights the importance of maintaining current software versions and implementing robust patch management processes, as this flaw represents a classic example of how legacy software components can remain vulnerable to exploitation for extended periods. Organizations should also consider implementing application whitelisting policies that restrict execution of untrusted PDF viewers and establish monitoring for suspicious document access patterns that may indicate exploitation attempts.