CVE-2021-32656: nextcloud nextcloud_server Improper Access Control
Vulnerability summary
CVE-2021-32656 is a high (CVSS 8.6) Improper Access Control vulnerability in nextcloud nextcloud_server. EPSS estimates a 1.84% chance of exploitation in the next 30 days, higher than 78.6% of scored vulnerabilities.
Timeline
- 01-06-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
Description
Nextcloud Server is a Nextcloud package that handles data storage. A vulnerability in federated share exists in versions prior to 19.0.11, 20.0.10, and 21.0.2. An attacker can gain access to basic information about users of a server by accessing a public link that a legitimate server user added as a federated share. This happens because Nextcloud supports sharing registered users with other Nextcloud servers, which can be done automatically when selecting the "Add server automatically once a federated share was created successfully" setting. The vulnerability is patched in versions 19.0.11, 20.0.10, and 21.0.2 As a workaround, disable "Add server automatically once a federated share was created successfully" in the Nextcloud settings.
CVSS metrics
3 scores · 2 sources · 2 versions- NVDNIST8.6HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
EPSS trend
Probability
1.84%
Chance of exploitation in the next 30 days
Percentile
79%
Versus all other CVEs
30-day change
0.00 pp
From 1.84% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Nextcloud2 products
- nextcloud_server< 19.0.11 | ≥ 20.0.0, < 20.0.10 | ≥ 21.0.0, < 21.0.2
- security-advisories< 19.0.11 | ≥ 20.0.0, < 20.0.10 | ≥ 21.0.0, < 21.0.2
1 vendor · 2 products
References
3 links- github.com/nextcloud/security-advisories/security/advisories/GHSA-j875-vr2q-h6x6X Refsource CONFIRMThird Party Advisory