CVE-2021-43802 : Vulnerability Insights and Analysis

Etherpad is a real-time collaborative editor. In versions prior to 1.8.16, an attacker can craft a malicious

.etherpad

file, allowing the attacker to gain admin privileges and execute arbitrary code on the Etherpad instance. This can have a critical impact on confidentiality, integrity, and availability.

Understanding CVE-2021-43802

What is CVE-2021-43802?

Etherpad is vulnerable to admin privilege escalation and arbitrary code execution through malicious imports. This occurs in versions below 1.8.16 due to improper validation, enabling an attacker to exploit the system.

The Impact of CVE-2021-43802

The vulnerability has a critical severity rating with a base score of 9.9 (CVSS v3.1), posing a high risk to confidentiality, integrity, and availability of the system.

Technical Details of CVE-2021-43802

Vulnerability Description

Attacker can craft a malicious

.etherpad

file for privilege escalation
Allows installation of a plugin for arbitrary code execution

Affected Systems and Versions

Product: etherpad-lite
Vendor: ether
Versions Affected: < 1.8.16

Exploitation Mechanism

Attacker triggers deletion of

express-session

state or waits for cleanup
Known attacks involve a plugin or custom cleanup process

Mitigation and Prevention

Immediate Steps to Take

Upgrade to version 1.8.16 or apply patches manually
Configure reverse proxies to reject

/p/*/import

requests
Limit users to read-only access
Prevent reuse of

express_sid

cookie values

Long-Term Security Practices

Regularly update software and plugins
Educate users on secure import practices

Patching and Updates

Apply all security patches promptly