Zulip is an open-source team chat application. Starting in version 10.0 and prior to version 10.3, the "Who can create public channels" access control mechanism can be circumvented by creating a private or web-public channel, and then changing the channel privacy to public. A similar technique works for creating private channels without permission, though such a process requires either the API or modifying the HTML, as we do mark the "private" radio button as disabled in such cases. Version 10.3 contains a patch.
https://zulip.readthedocs.io/en/latest/overview/changelog.html#zulip-server-10-3
https://zulip.com/help/configure-who-can-create-channels
https://github.com/zulip/zulip/security/advisories/GHSA-rqg7-xfqg-v7q5
https://github.com/zulip/zulip/commit/d2ff4bda4c3efa30fc3ab1f151255cfdbf370f78
Published: 2025-05-16
Updated: 2025-05-16
Base Score: 5
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:N/A:N
Severity: Medium
Base Score: 4.3
Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Severity: Medium
Base Score: 5.3
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Severity: Medium
EPSS: 0.00039