CVE-2025-66556: Nextcloud talk allows participants to blindly delete poll drafts of other users by ID

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-05 · updated 2026-10-15
Weakness: CWE-639

Description

Nextcloud talk is a video & audio conferencing app for Nextcloud. Prior to 20.1.8 and 21.1.2, a participant with chat permissions was able to delete poll drafts of other participants within the conversation based on their numeric ID. This vulnerability is fixed in 20.1.8 and 21.1.2.

Affected products

Nextcloud Talk: from 20.0.0 before 20.1.8; from 21.0.0 before 21.1.2 — fixed in 20.1.8, 21.1.2

How to fix

Upgrade to a fixed version: Nextcloud Talk 20.1.8, 21.1.2. Check the vendor advisory for mitigations.

References

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-pr9f-vqgg-m2jh
https://github.com/nextcloud/spreed/commit/bd68e80d1dea98d84c1d621c2c681238cf041725
https://github.com/nextcloud/spreed/pull/15532
https://hackerone.com/reports/3247386

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