CVE-2016-4427
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 · uneditedIn zulip before 1.3.12, deactivated users could access messages if SSO was enabled.
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 confidenceIn Zulip before version 1.3.12, when SSO authentication is enabled, the application fails to properly validate whether a user account has been deactivated during the SSO login process. This allows previously deactivated users to bypass access controls and view messages they should no longer have access to.
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< 1.3.12CVSS 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
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 checksWork through these to decide whether this CVE applies to you.
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Determine installed Zulip versionCheck the Zulip version file or run 'zulip --version' from the Zulip server. On self-hosted installations, look for a VERSION file in the Zulip directory or check the package.json for the version number.Affected if The installed version is below 1.3.12
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Verify if SSO authentication is enabledExamine the Zulip configuration settings (typically in /etc/zulip/settings.py or through the admin interface). Look for authentication backends configuration - specifically check if any SSO provider (such as SAML, LDAP, or OAuth) is listed as an active authentication method.Affected if SSO authentication is enabled and the Zulip version is below 1.3.12
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Identify deactivated users with accessQuery the Zulip database (PostgreSQL) for user accounts that have 'is_active' set to false but have recent authentication events. Run: SELECT email, date_joined, last_login FROM zerver_userprofile WHERE is_active = false ORDER BY last_login DESC; Compare login timestamps to identify any deactivated users who have logged in after deactivation.Affected if There are deactivated user accounts that have authenticated (logged in) after being deactivated, when using SSO authentication
You are affected if Zulip version is below 1.3.12, SSO authentication is enabled, and previously deactivated users have been able to successfully authenticate and access the system.
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.
dbcve · scoped1.3.12
Upgrade to Zulip version 1.3.12 or later, which implements proper validation of user activation status during SSO authentication.
Zulip 1.3.12
- Back up the Zulip database and configuration files before proceeding
- Stop the Zulip server to prevent data inconsistency during upgrade
- Update to Zulip version 1.3.12 or later. For installations using git: 'git pull' and checkout the release tag 1.3.12. For package installations: upgrade via your package manager
- Run database migrations: 'python manage.py migrate'
- Restart the Zulip server
- Verify that deactivated users can no longer access messages when SSO is enabled
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-4427 — 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-2016-4427 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
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