CVE-2021-43799 : Exploit Details and Defense Strategies

Zulip Server prior to version 4.9 exposes weak default secrets on ports, allowing remote attackers to execute code and intercept message traffic.

Understanding CVE-2021-43799

Zulip Server's vulnerable versions expose RabbitMQ ports with weak default secrets, posing a high severity threat.

What is CVE-2021-43799?

Zulip Server installs RabbitMQ, which opens ports without proper access control. Weak entropy in RabbitMQ's default 'cookie' allows attackers to execute code and intercept messages.

The Impact of CVE-2021-43799

High Severity: CVSS base score of 8.6
Confidentiality Impact: High
Attack Vector: Network
No Integrity Impact: Limited scope of impact but critical data exposure

Technical Details of CVE-2021-43799

Zulip Server's vulnerability to expose weak secrets on RabbitMQ ports carries significant risks.

Vulnerability Description

The weak PRNG in RabbitMQ's default 'cookie' leads to only 20 bits of entropy, enabling brute-force attacks.

Affected Systems and Versions

Product: Zulip
Vendor: Zulip
Versions Affected: < 4.9
Version 4.9 contains the patch for this vulnerability.

Exploitation Mechanism

Attack Complexity: Low
Privileges Required: None
Impact Scope: Changed
Attack Vector: Network

Mitigation and Prevention

Addressing the vulnerability requires immediate and long-term security measures.

Immediate Steps to Take

Apply the patch by upgrading to Zulip Server version 4.9
Configure firewalls to restrict access to ports 5672 and 25672 from outside the server

Long-Term Security Practices

Regularly update Zulip Server to the latest versions
Implement proper network segmentation and access controls

Patching and Updates

Version 4.9 includes the necessary patch to mitigate the vulnerability.