{"id":"CVE-2021-32656","aliases":["EUVD-2021-19476","GHSA-j875-vr2q-h6x6"],"status":"published","title":"Trusted servers exchange can be triggered by attacker","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.","severity":{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.01841,"percentile":0.79171,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-284"],"published":"2021-06-01T21:45:11Z","modified":"2026-10-24T10:30:59Z","products":[{"vendor":"kiteworks","product":"security-advisories"},{"vendor":"nextcloud","product":"nextcloud_server"},{"vendor":"nextcloud","product":"security-advisories"}],"references":[{"url":"https://github.com/nextcloud/security-advisories/security/advisories/GHSA-j875-vr2q-h6x6","tags":["x_refsource_CONFIRM","x_transferred","Third Party Advisory","advisory"]},{"url":"https://hackerone.com/reports/1167853","tags":["x_refsource_MISC","x_transferred","Permissions Required","Third Party Advisory","report"]},{"url":"https://security.gentoo.org/glsa/202208-17","tags":["vendor-advisory","x_refsource_GENTOO","x_transferred","Third Party Advisory","advisory"]}],"sources":{"cve":[{"id":"CVE-2021-32656","title":"Trusted servers exchange can be triggered by attacker","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.","status":"published","published":"2021-06-01T21:45:11Z","modified":"2024-08-03T23:25:31.075Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-284"],"updated_at":"2026-11-02T14:33:07.014772Z"}],"euvd":[{"id":"EUVD-2021-19476","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.","status":"published","published":"2021-06-01T21:45:11Z","modified":"2024-08-03T23:25:31Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N","level":"high"}],"updated_at":"2026-11-03T03:24:35.855495Z"}],"nvd":[{"id":"CVE-2021-32656","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.","status":"published","published":"2021-06-01T22:15:08.173Z","modified":"2026-06-17T03:53:21.657Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N","level":"high","assessor":"secondary"},{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N","level":"high","assessor":"primary"},{"version":"2.0","score":5,"vector":"AV:N/AC:L/Au:N/C:P/I:N/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-284"],"updated_at":"2026-11-02T14:06:53.987491Z"}],"osv":[{"id":"CVE-2021-32656","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.","status":"published","published":"2021-06-01T22:15:08.173Z","modified":"2026-10-24T10:30:59.318526427Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N","level":"high"}],"updated_at":"2026-11-02T15:44:19.793849Z"}]}}