CVE-2021-30479
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 · uneditedAn issue was discovered in Zulip Server before 3.4. A bug in the implementation of the all_public_streams API feature resulted in guest users being able to receive message traffic to public streams that should have been only accessible to members of the organization.
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 confidenceA broken access control vulnerability in Zulip Server's all_public_streams API feature allowed guest users to receive message traffic from public streams that should only be visible to full organization members. This resulted in unauthorized information disclosure to guest users who should have been excluded from these streams.
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< 3.4CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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 checksWork through these to decide whether this CVE applies to you.
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Identify your Zulip Server versionAccess the Zulip administration interface or check the server's package/version information to determine the installed Zulip Server version number.Affected if The installed version is any release prior to version 3.4 (for example, 3.3.x, 3.2.x, or earlier).
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Confirm guest users exist in your organizationReview your Zulip organization's user list to identify whether any user accounts are configured with the guest role, which provides limited visibility compared to full members.Affected if Your Zulip organization contains one or more guest user accounts.
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Determine if all_public_streams API is accessible to guestsInspect the organization's permission settings and API access controls to verify whether the all_public_streams endpoint or feature is exposed to or usable by guest user accounts.Affected if The all_public_streams API feature is enabled and accessible to guest users in your configuration.
You are affected if your Zulip Server version is below 3.4, your organization has guest users, and the all_public_streams API feature is accessible to those guest users, allowing them to view public stream messages they should not see.
Generated from the published advisory. Verify against your own configuration.
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 data3.4
Upgrade Zulip Server to version 3.4 or later, which contains the fix for this authorization bypass. Alternatively, if upgrading is not immediately possible, review and restrict the all_public_streams API permissions configuration to prevent guest user access.
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-30479 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-30479 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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