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CVE-2021-32689highCWE-200CWE-708

Nextcloud Talk not properly disassociating users from chats after account deletion

21Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 8.1epss 1.0%
exploitation probability
1.0%top 40% of all CVEs
observed exploitation
nono source reports it
In short

When a Nextcloud Talk user account is deleted, their username can be reused by a new account, allowing the new user to access chat messages that were sent to the previous account holder. This means private conversations could be exposed to unauthorized people.

Technical detail

Nextcloud Talk fails to disassociate deleted user accounts from chat message history, allowing username reuse to grant access to previous conversations. The vulnerability requires an attacker to create an account using a previously deleted username; pre-conditions include systems where user-chosen usernames are permitted. Impact includes unauthorized access to chat messages (CWE-200) and improper resource cleanup (CWE-708).

Summary generated and translated by AI from the official description.
Nextcloud Talk is a fully on-premises audio/video and chat communication service. In versions prior to 11.2.2, if a user was able to reuse an earlier used username, they could get access to any chat message sent to the previous user with this username. The issue was patched in versions 11.2.2 and 11.3.0. As a workaround, don't allow users to choose usernames themselves. This is the default behaviour of Nextcloud, but some user providers may allow doing so.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Affected products
nextcloud · security-advisories
References
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-xv6f-344w-895chttps://github.com/nextcloud/spreed/pull/5633https://github.com/nextcloud/spreed/releases/tag/v11.2.2https://github.com/nextcloud/spreed/releases/tag/v11.3.0https://hackerone.com/reports/1200700