CVE intelligence and bounded remediation

CVE-2016-9464 — Nextcloud Server before 9.0.54 and 10.0.0 suffers from an improper authorization check on removing shares

Medium CVSS 4.3

Nextcloud Server before 9.0.54 and 10.0.0 suffers from an improper authorization check on removing shares. The Sharing Backend as implemented in Nextcloud does differentiate between shares to users and groups. In case of a received group share, users should be able to unshare the file to themselves but not to the whole group. The previous API implementation simply unshared the file to all users in the group.

Severity
Medium
CVSS
4.3 (3.0)
Published
2017-03-28
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-285

Affected products

  • nextcloud / nextcloud_server
  • nextcloud / nextcloud_server / 10.0

Matched remediation archetype

Authorization bypass, IDOR, and cross-tenant access

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Check exposure

  • Map object and action authorization checks across API, UI, batch, import/export, and background-job paths.
  • Identify tenant, ownership, role, and policy boundaries for affected resources and administrative operations.
  • Use synthetic fixtures to compare intended access matrices without accessing another user's real data.

Remediate safely

  • Enforce server-side authorization at each resource access and state transition using the authenticated principal and trusted tenant context.
  • Scope data queries by tenant and ownership; treat client-supplied identifiers, roles, and policy claims as untrusted.
  • Add deny-by-default policy tests for horizontal and vertical access across every affected transport.

Authoritative sources

Complete CVE record and remediation plan

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