Nextcloud Server before 9.0.55 and 10.0.2 suffers from a permission increase on re-sharing via OCS API issue. A permission related issue within the OCS sharing API allowed an authenticated adversary to reshare shared files with an increasing permission set. This may allow an attacker to edit files in a share despite having only a 'read' permission set. Note that this only affects folders and files that the adversary has at least read-only permissions for.
Severity
CVSS 3.0
6.4 medium
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
EPSS
0.6% chance of exploitation in the next 30 days; higher than 48% of CVEs (scores of 2026-10-31)