CVE-2021-30479: Zulip Server

Medium severity, CVSS 5.3. EPSS: 0.9% chance of exploitation in the next 30 days.

An issue was discovered in Zulip Server before 3.4. A bug in the implementation of the all_public_streams API feature resulted in guest users being able to receive message traffic to public streams that should have been only accessible to members of the organization.

Affected products

• Zulip Zulip Server: before 3.4 (fixed in 3.4)

Published 2021-04-15. Last modified 2026-06-17.