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Fencer Vulns
high 8.6

CVE-2021-32656 json

Trusted servers exchange can be triggered by attacker

published 2021-06-01 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-19476

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.8%
EPSS 1.8% chance of exploitation in 30 days, percentile 79%
public exploits
0
none known

Summary

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.

Patch / fix

  • nextcloud nextcloud_server 19.0.11, 20.0.10, 21.0.2
  • nextcloud Arch Linux 21.0.2-1

arch linux advisories AVG-2024

Exploit prediction

1.84% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
NVD 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:P/I:N/A:N

Affected products

  • nextcloud security-advisories

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.