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DeckApplication · Nextcloud

CVE-2021-22913

MEDIUM · 6.5 CVSS v3.1 Published 2021-06-11
Fix available
A fix is available. Upgrade to 1.2.7 / 1.4.1 or later.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

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
Nextcloud Deck before 1.2.7, 1.4.1 suffers from an information disclosure vulnerability when searches for sharees utilize the lookup server by default instead of only the local Nextcloud server unless a global search has been explicitly chosen by the user.

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

Nextcloud Deck before versions 1.2.7 and 1.4.1 contains an information disclosure vulnerability where sharee searches (searching for users or groups to share content with) query an external lookup server by default rather than restricting queries to only the local Nextcloud server. This exposes user account existence information to external parties unless users explicitly select a local-only search.

MitigationUpgrade Nextcloud Deck to version 1.2.7, 1.4.1, or later where the default search behavior was changed to query only the local server. Alternatively, ensure users explicitly choose local-only searches when sharing content.

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
DeckApplication
Affected:< 1.2.7>= 1.3.0, < 1.4.1

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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 Deck app version
    Navigate to Nextcloud admin panel > Apps > Deck, or inspect the app's info.xml file in the Deck app directory. Look for the version number.
    Affected if The installed version is less than 1.2.7, or greater than or equal to 1.3.0 but less than 1.4.1
  2. Verify sharee search functionality is accessible
    Log in as a user with permission to share content in Deck. Attempt to share a card or board and access the user/group search field to see if lookup functionality is available.
    Affected if The sharee search feature is accessible to users, enabling the vulnerable behavior to trigger
  3. Check for external lookup server configuration
    Inspect Nextcloud's config/config.php file or Deck's app configuration for settings related to lookup server, user lookup, or federated search (keywords: lookup_server, user_search, federation).
    Affected if An external lookup server is configured and enabled by default, causing user searches to leak to external parties
  4. Confirm search behavior defaults to external lookup
    As a user with sharing rights, perform a sharee search without explicitly restricting to local search. Observe whether the search queries an external server (may appear as network requests to non-local domains).
    Affected if The default search behavior queries external servers rather than only the local Nextcloud instance

A user is affected if Nextcloud Deck version is in the vulnerable range AND sharee searches are performed without explicit local-only restriction, causing user account existence to be disclosed to external lookup servers.

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 1.2.7 / 1.4.1 or later
Fixed in 1.2.71.4.1
Interim mitigation

Upgrade Nextcloud Deck to version 1.2.7, 1.4.1, or later where the default search behavior was changed to query only the local server. Alternatively, ensure users explicitly choose local-only searches when sharing content.

Fix this in Deck Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

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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-2021-22913 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