CVE-2021-39859 : Exploit Details and Defense Strategies

This article provides details about the CVE-2021-39859 vulnerability affecting Adobe Acrobat Reader DC.

Understanding CVE-2021-39859

This section dives into the specifics of the Use After Free vulnerability in Adobe Acrobat Reader DC.

What is CVE-2021-39859?

CVE-2021-39859 refers to a Use After Free vulnerability in Adobe Acrobat Reader DC versions 2021.005.20060 and earlier. This flaw could result in the disclosure of sensitive memory, with potential exploitation to bypass mitigations like ASLR by malicious actors. Exploitation necessitates user interaction through the opening of a malicious file.

The Impact of CVE-2021-39859

The vulnerability has a CVSSv3 base score of 5.5, marked as medium severity. Specific impacts include:

Low attack complexity and vector
High confidentiality impact
No integrity and availability impact
User interaction required for exploitation

Technical Details of CVE-2021-39859

This section outlines the technical aspects of the CVE-2021-39859 vulnerability.

Vulnerability Description

The vulnerability is categorized as a Use After Free (CWE-416) flaw, leading to potential memory disclosure in affected Adobe Acrobat Reader DC versions.

Affected Systems and Versions

Product: Acrobat Reader
Vendor: Adobe
Affected Versions:
2021.005.20060 and earlier
2020.004.30006 and earlier
2017.011.30199 and earlier

Exploitation Mechanism

The exploitation of this vulnerability requires a victim to open a malicious file, subsequently triggering the Use After Free flaw.

Mitigation and Prevention

Insights into addressing and mitigating the impacts of CVE-2021-39859.

Immediate Steps to Take

Update Adobe Acrobat Reader DC to the latest version
Be cautious while opening files from untrusted sources

Long-Term Security Practices

Regularly update software and applications
Implement security best practices to avoid interacting with suspicious files

Patching and Updates

Adobe has released a security advisory (APSB21-55) addressing this vulnerability