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OwncloudApplication

CVE-2020-28645

CRITICAL · 9.1 CVSS v3.1 Published 2021-02-09
Fix available
A fix is available. Upgrade to 10.6.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges 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
Deleting users with certain names caused system files to be deleted. Risk is higher for systems which allow users to register themselves and have the data directory in the web root. This affects ownCloud/core versions < 10.6.

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 · high confidence

A path traversal vulnerability in ownCloud core versions prior to 10.6 allows deletion of system files when users with specially crafted names (likely containing directory traversal sequences like '../') are deleted. The vulnerability is exploitable when self-registration is enabled and the data directory resides within the web root, allowing attackers to potentially delete arbitrary files on the server.

MitigationUpgrade ownCloud/core to version 10.6 or later. Additionally, disable user self-registration and ensure the data directory is placed outside the web root.

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
OwncloudApplication
Affected:< 10.6.0

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
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

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

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. Determine installed ownCloud core version
    Locate the version.php or version file in the ownCloud installation directory, or check the ownCloud admin panel under Settings > General for the current version number
    Affected if The installed version is any release prior to 10.6.0 (e.g., 10.5.x, 10.4.x, etc.)
  2. Verify if user self-registration is enabled
    Navigate to ownCloud admin panel > Settings > General > User Authentication, or inspect the config/config.php file for the 'allow_user_to_change_display_name' or registration app settings
    Affected if Self-registration is enabled and allows new users to sign up without admin intervention
  3. Locate the data directory configuration
    Inspect the config/config.php file for the 'datadirectory' parameter, or check the ownCloud admin panel for the data folder path
    Affected if The data directory path is inside the web root (e.g., /var/www/html/owncloud/data or similar) rather than outside the web root (e.g., /var/www/owncloud-data)

You are affected if running ownCloud core version below 10.6.0 AND self-registration is enabled AND the data directory is located within the web root, allowing a crafted username with traversal sequences to delete files outside the intended user storage.

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.

dbcve · scoped
Upgrade available Upgrade to 10.6.0 or later
Fixed in 10.6.0
Interim mitigation

Upgrade ownCloud/core to version 10.6 or later. Additionally, disable user self-registration and ensure the data directory is placed outside the web root.

Recommended fix High confidence

ownCloud 10.6.0

  1. Ensure you have a complete backup of your ownCloud instance, including database and data directory, before upgrading
  2. Review the ownCloud 10.6.0 release notes for any specific upgrade requirements or migration steps
  3. Put your ownCloud server into maintenance mode to prevent data changes during upgrade
  4. Upgrade ownCloud to version 10.6.0 using your package manager or the official upgrade path documented at owncloud.com
  5. After upgrade completes, verify the installation by logging in as an administrator
  6. Confirm that user deletion no longer causes unintended file system deletion
  7. Take the server out of maintenance mode and monitor for any issues
Caveat Review ownCloud 10.6.0 release notes; minor version upgrades typically have low risk but always test in staging first

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Owncloud Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2020-28645 in production — separate from our analysis above.

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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