Auth bypass in Nextcloud Security-Advisories
CVE-2025-66556
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.
Vulnerability class: IDOR (Insecure Direct Object Reference)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 3.5 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (15.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Nextcloud Security-Advisories — versions < 20.1.8, >= 21.0.0-beta.1, < 21.1.2
- Nextcloud Talk
Weakness classification (CWE)
References
- github.com/nextcloud/security-advisories/security/advisories/GHSA-pr9f-vqgg-m2jh (Patch, Vendor Advisory)
- github.com/nextcloud/spreed/pull/15532 (Patch, Issue Tracking)
- github.com/nextcloud/spreed/commit/bd68e80d1dea98d84c1d621c2c681238cf041725 (Patch)
- hackerone.com/reports/3247386 (Issue Tracking, Vendor Advisory)
Frequently asked questions
- What is CVE-2025-66556?
- CVE-2025-66556 is a low-severity vulnerability in Nextcloud Security-Advisories, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 3.5/10. Published 2025-12-05.
- How severe is CVE-2025-66556?
- Low severity. CVSS v3 base score is 3.5 out of 10.