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Nextcloud ServerApplication · Nextcloud

CVE-2019-15621

MEDIUM · 6.5 CVSS v3.1 Published 2020-02-04
Fix available
A fix is available. Upgrade to 14.0.13 / 15.0.9 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Improper permissions preservation in Nextcloud Server 16.0.1 causes sharees to be able to reshare with write permissions when sharing the mount point of a share they received, as a public link.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Nextcloud Server 16.0.1 has an improper permissions preservation issue in its sharing functionality. When a sharee receives a share that is a mount point and attempts to reshare it as a public link, the system fails to properly enforce the original share's permission restrictions, allowing write permissions to be granted when they should not be.

MitigationUpgrade to Nextcloud Server 16.0.2 or later where this permission preservation issue has been fixed.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Nextcloud ServerApplication
Affected:< 14.0.13>= 15.0.0, < 15.0.9>= 16.0.0, < 16.0.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Nextcloud Server version
    Run 'occ --version' from the Nextcloud installation directory, or inspect version.php in the Nextcloud root directory, or check the 'version' entry in config/config.php
    Affected if Version is < 14.0.13, OR >= 15.0.0 and < 15.0.9, OR >= 16.0.0 and < 16.0.2
  2. Verify sharing is enabled
    Run 'occ app:list' and confirm the files_sharing app is enabled, or check the Nextcloud admin web interface under Apps
    Affected if The files_sharing app is enabled (required for vulnerability to be exploitable)
  3. Check for reshareable shares
    Query the oc_share table in the Nextcloud database: SELECT * FROM oc_share WHERE reshared IS NOT NULL or check shares where the sharee has reshare permissions (permissions field includes 31)
    Affected if Users have received shares that they can reshare (sharee has reshare permission)

Environment is affected if the installed Nextcloud Server version is in the vulnerable ranges AND sharing is enabled with reshareable shares present in the system.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to 14.0.13 / 15.0.9 / 16.0.2 or later
Fixed in 14.0.1315.0.916.0.2
Interim mitigation

Upgrade to Nextcloud Server 16.0.2 or later where this permission preservation issue has been fixed.

Fix this in Nextcloud Server Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-15621 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data