CVE-2021-30478

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-04-15 · updated 2026-06-17
Weakness: CWE-269

Description

An issue was discovered in Zulip Server before 3.4. A bug in the implementation of the can_forge_sender permission (previously is_api_super_user) resulted in users with this permission being able to send messages appearing as if sent by a system bot, including to other organizations hosted by the same Zulip installation.

Affected products

zulip: before 3.4 — fixed in 3.4

How to fix

Upgrade to a fixed version: zulip 3.4. Check the vendor advisory for mitigations.

References

https://blog.zulip.com/2021/04/14/zulip-server-3-4/
https://blog.zulip.com/2021/04/14/zulip-server-3-4/

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