Zulip non-admins can invite new users to streams they would not otherwise be able to add existing users to

Vulnerability Description

Zulip is an open-source team collaboration tool. A vulnerability in version 8.0 is similar to CVE-2023-32677, but applies to multi-use invitations, not single-use invitation links as in the prior CVE. Specifically, it applies when the installation has configured non-admins to be able to invite users and create multi-use invitations, and has also configured only admins to be able to invite users to streams. As in CVE-2023-32677, this does not let users invite new users to arbitrary streams, only to streams that the inviter can already see. Version 8.1 fixes this issue. As a workaround, administrators can limit sending of invitations down to users who also have the permission to add users to streams.

References

• https://github.com/zulip/zulip/security/advisories/GHSA-87p9-wprh-7rm6
• https://github.com/zulip/zulip/security/advisories/GHSA-mrvp-96q6-jpvc
• https://github.com/zulip/zulip/commit/0df7bd71f32f3b772e2646c6ab0d60c9b610addf
• https://zulip.com/help/configure-who-can-invite-to-streams
• https://zulip.com/help/restrict-account-creation#change-who-can-send-invitations