Auth bypass in Nextcloud Server
CVE-2021-32688
Nextcloud Server is a Nextcloud package that handles data storage. Nextcloud Server supports application specific tokens for authentication purposes. These tokens are supposed to be granted to a specific applications (e.g. DAV sync clients), and can also be configured by the user to not have any filesystem access. Due to a lacking permission check, the tokens were able to change their own permissions in versions prior to 19.0.13, 20.0.11, and 21.0.3. Thus fileystem limited tokens were able to grant themselves access to the filesystem. The issue is patched in versions 19.0.13, 20.0.11, and 21.0.3. There are no known workarounds aside from upgrading.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.023 (83.1th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 83rd percentile — 83.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.023 · newest: 0.023 · change: 0.000
Affected products
- Nextcloud Server
- Nextcloud Security-Advisories — versions < 19.0.13, >= 20.0.0, < 20.0.11, >= 21.0.0, < 21.0.3
- Fedoraproject Fedora — versions 33, 34
Weakness classification (CWE)
References
- github.com/nextcloud/security-advisories/security/advisories/GHSA-48m7-7r2r-838r (Third Party Advisory)
- github.com/nextcloud/server/pull/27000 (Patch, Third Party Advisory)
- hackerone.com/reports/1193321 (Permissions Required)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- security.gentoo.org/glsa/202208-17 (vendor-advisory, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-32688?
- CVE-2021-32688 is a high-severity vulnerability in Nextcloud Server, classified under Improper Authorization. CVSS score: 8.8/10. Published 2021-07-12.
- How severe is CVE-2021-32688?
- High severity. CVSS v3 base score is 8.8 out of 10.