CVE-2021-28552 in Acrobat Reader
Summary
by MITRE • 08/25/2021
Acrobat Reader DC versions versions 2021.001.20155 (and earlier), 2020.001.30025 (and earlier) and 2017.011.30196 (and earlier) are affected by an Use After Free vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.
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Analysis
by VulDB Data Team • 08/29/2021
The vulnerability identified as CVE-2021-28552 represents a critical use after free flaw in Adobe Acrobat Reader DC across multiple version ranges including 2021.001.20155 and earlier, 2020.001.30025 and earlier, and 2017.011.30196 and earlier. This type of vulnerability falls under the Common Weakness Enumeration category CWE-416, which specifically addresses the use of memory after it has been freed, creating potential for memory corruption and arbitrary code execution. The flaw exists within the document processing components of Acrobat Reader DC, specifically when handling maliciously crafted PDF files that trigger improper memory management during document parsing operations.
The technical exploitation of this vulnerability requires an attacker to craft a specially designed PDF file that, when opened by a victim using an affected version of Acrobat Reader DC, triggers the use after free condition. This occurs during the parsing or rendering of the malicious document where the application attempts to access memory that has already been deallocated, potentially allowing an attacker to manipulate the memory layout and execute arbitrary code with the privileges of the current user. The vulnerability necessitates user interaction as the victim must actively open the malicious file, making it a client-side attack vector that relies on social engineering or phishing techniques to succeed.
From an operational impact perspective, this vulnerability poses significant risks to enterprise environments where Acrobat Reader DC is widely deployed for document viewing and processing. The arbitrary code execution capability allows attackers to potentially install malware, steal sensitive data, establish persistence mechanisms, or escalate privileges within the victim's system. The fact that exploitation requires user interaction limits the automated attack surface but does not eliminate the threat, as successful exploitation can lead to complete system compromise. Organizations running affected versions face potential data breaches, unauthorized access to sensitive documents, and possible lateral movement within their networks through the compromised user accounts.
Mitigation strategies for CVE-2021-28552 should prioritize immediate patching of all affected Acrobat Reader DC installations to the latest versions provided by Adobe. Security administrators should implement strict document filtering policies that prevent execution of potentially malicious files, particularly PDFs from untrusted sources. Network-based defenses such as web application firewalls and content filtering solutions can help block malicious PDF files before they reach end-user systems. Additionally, user education programs should emphasize the importance of not opening unexpected or suspicious PDF attachments, and organizations should consider implementing sandboxing technologies for PDF processing to contain potential exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1566 for phishing campaigns, making comprehensive defense-in-depth strategies essential for protecting against exploitation attempts.