CVE-2021-43799: RabbitMQ exposes ports with weak default secrets in Zulip Server
First published: Tue Jan 25 2022(Updated: )
Zulip is an open-source team collaboration tool. Zulip Server installs RabbitMQ for internal message passing. In versions of Zulip Server prior to 4.9, the initial installation (until first reboot, or restart of RabbitMQ) does not successfully limit the default ports which RabbitMQ opens; this includes port 25672, the RabbitMQ distribution port, which is used as a management port. RabbitMQ's default "cookie" which protects this port is generated using a weak PRNG, which limits the entropy of the password to at most 36 bits; in practicality, the seed for the randomizer is biased, resulting in approximately 20 bits of entropy. If other firewalls (at the OS or network level) do not protect port 25672, a remote attacker can brute-force the 20 bits of entropy in the "cookie" and leverage it for arbitrary execution of code as the rabbitmq user. They can also read all data which is sent through RabbitMQ, which includes all message traffic sent by users. Version 4.9 contains a patch for this vulnerability. As a workaround, ensure that firewalls prevent access to ports 5672 and 25672 from outside the Zulip server.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Zulip Desktop | <4.9 |
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Reference Links
Frequently Asked Questions
What is CVE-2021-43799?
CVE-2021-43799 is a vulnerability in Zulip Server that allows for unrestricted access to RabbitMQ ports.
What is the severity of CVE-2021-43799?
CVE-2021-43799 has a severity level of 9.8 (critical).
How does CVE-2021-43799 affect Zulip Server?
CVE-2021-43799 affects Zulip Server versions prior to 4.9 and allows RabbitMQ to open default ports without restrictions.
What is the fix for CVE-2021-43799?
The fix for CVE-2021-43799 is to upgrade to Zulip Server version 4.9 or later.
Are there any references for CVE-2021-43799?
Yes, you can find more information on CVE-2021-43799 at the following references: [Link 1](https://github.com/gteissier/erl-matter), [Link 2](https://github.com/zulip/zulip/commit/a5496f4098e3998c9b84e8dc564aa983d6cdf6e8), [Link 3](https://github.com/zulip/zulip/releases/tag/4.9).
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