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Zulip ServerApplication · Zulip

CVE-2023-32678

MEDIUM · 6.5 CVSS v3.1 Published 2023-08-25
Fix available
A fix is available. Upgrade to 7.3 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
Zulip is an open-source team collaboration tool with topic-based threading that combines email and chat. Users who used to be subscribed to a private stream and have been removed from it since retain the ability to edit messages/topics, move messages to other streams, and delete messages that they used to have access to, if other relevant organization permissions allow these actions. For example, a user may be able to edit or delete their old messages they posted in such a private stream. An administrator will be able to delete old messages (that they had access to) from the private stream. This issue was fixed in Zulip Server version 7.3.

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

Zulip fails to properly revoke message permissions when users are removed from private streams. Users who were previously subscribed to a private stream retain the ability to edit, move, and delete messages they previously had access to even after removal, due to stale authorization checks.

MitigationUpgrade to Zulip Server version 7.3 or later. Review existing user access to private streams and revoke any lingering permissions for former members.

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
Zulip ServerApplication
Affected:< 7.3

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 Zulip Server version
    Run `zulip --version` or check the `/zulip-version` endpoint, or inspect the version file in the Zulip installation directory
    Affected if The installed version is lower than 7.3
  2. Identify private streams with former members
    Query the database or use admin API to list all private streams and review their subscription history, looking for users who were previously subscribed but are now removed
    Affected if There are private streams where users were previously members and have been removed
  3. Verify message action capabilities for former members
    As a test, attempt to edit, move, or delete a message in a previously-subscribed private stream using a user account that was removed from that stream
    Affected if The removed user can still successfully edit, move, or delete messages in the private stream they were removed from
  4. Review authorization audit logs
    Examine Zulip's server logs or audit records for message actions (edit/move/delete) performed by users who are no longer members of the private stream where the messages reside
    Affected if There are records of former private stream members performing message operations on messages in streams they no longer belong to

You are affected if running Zulip Server version below 7.3 AND there are former private stream members who can still perform edit/move/delete actions on messages in streams they were removed from.

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 7.3 or later
Fixed in 7.3
Interim mitigation

Upgrade to Zulip Server version 7.3 or later. Review existing user access to private streams and revoke any lingering permissions for former members.

Recommended fix High confidence

Zulip Server 7.3 or later

  1. 1. Back up the current Zulip Server installation and database before upgrading
  2. 2. Consult the official Zulip upgrade documentation at zulip.readthedocs.io for your current version
  3. 3. Upgrade to Zulip Server version 7.3 or later using the recommended upgrade procedure for your deployment method
  4. 4. After upgrade, verify that users previously removed from private streams can no longer access or modify messages in those streams
  5. 5. Test that private stream permissions are properly enforced for all users
Caveat Check Zulip release notes for version 7.3 for any breaking changes between your current version and 7.3

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

Fix this in Zulip Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

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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-2023-32678 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