CVE-2021-39856 Explained : Impact and Mitigation

Adobe Acrobat Reader DC NTLMv2 SSO Information Disclosure via LoadFile

Understanding CVE-2021-39856

Acrobat Reader DC ActiveX Control versions 2021.005.20060 (and earlier), 2020.004.30006 (and earlier), and 2017.011.30199 (and earlier) are affected by an Information Disclosure vulnerability. An unauthenticated attacker could leverage this vulnerability to obtain NTLMv2 credentials. Exploitation of this issue requires user interaction in that a victim must visit an attacker controlled web page.

What is CVE-2021-39856?

Vulnerability in Adobe Acrobat Reader DC ActiveX Control
Allows unauthenticated attackers to obtain NTLMv2 credentials
Requires victim's interaction by visiting a malicious website

The Impact of CVE-2021-39856

CVSS Base Score: 6.5 (Medium Severity)
Attack Vector: Network
Confidentiality Impact: High
User Interaction Required: Yes

Technical Details of CVE-2021-39856

Adobe Acrobat Reader DC ActiveX Control is affected by an information disclosure vulnerability.

Vulnerability Description

NTLMv2 SSO Information Disclosure via LoadFile

Affected Systems and Versions

Adobe Acrobat Reader affected versions:
Versions less than or equal to 2021.005.20060
Versions less than or equal to 2020.004.30006
Versions less than or equal to 2017.011.30199

Exploitation Mechanism

Unauthenticated attacker can exploit by luring victims to a malicious website

Mitigation and Prevention

It's crucial to take immediate steps and implement long-term security measures to mitigate the risk of this vulnerability.

Immediate Steps to Take

Update Adobe Acrobat Reader to the latest version
Avoid visiting untrusted websites
Be cautious of unexpected links and downloads

Long-Term Security Practices

Regularly update software and security patches
Educate users on safe browsing practices
Implement network security measures

Patching and Updates

Adobe has released patches to address this vulnerability
Users should update to the patched versions