Nextcloud ServerApplication · Nextcloud
CVE-2018-3775
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 · uneditedImproper Authentication in Nextcloud Server prior to version 12.0.3 would allow an attacker that obtained user credentials to bypass the 2 Factor Authentication.
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 confidenceThis is a 2FA bypass vulnerability in Nextcloud Server where an attacker who has obtained valid user credentials (through phishing, credential leaks, or other means) can bypass the two-factor authentication mechanism and gain full access to the user's account without completing the second authentication factor.
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
Nextcloud ServerApplication
< 12.0.3CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/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 checksWork through these to decide whether this CVE applies to you.
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Determine installed Nextcloud Server versionAccess the Nextcloud admin panel and navigate to Administration > Settings > Overview, or check the version.php file in the Nextcloud installation directory under /config/Affected if The displayed version is any version prior to 12.0.3 (for example, 12.0.2, 12.0.1, 12.0.0, or earlier major versions)
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Verify if two-factor authentication is enabledGo to Administration > Security in the Nextcloud admin panel and check if 'Two-Factor Authentication' is enforced or enabled for usersAffected if Two-factor authentication is enabled or enforced in the Nextcloud settings
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Review recent authentication events for anomaliesAccess the Nextcloud admin panel logging section or review the Nextcloud log files (typically located in /data/nextcloud.log or configured log directory) for login events around the time of concernAffected if There are successful login events using usernames that also have 2FA enabled, without corresponding 2FA completion records in the logs
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Check for unexpected user sessionsIn the Nextcloud admin panel, navigate to Administration > User management > Sessions to view active and recent sessions for all usersAffected if There are sessions active or recorded for users with 2FA enabled that show no 2FA challenge completion
You are affected if your Nextcloud Server version is below 12.0.3 AND two-factor authentication is enabled in your environment, as this combination allows the 2FA bypass to be exploited.
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 data12.0.3
Upgrade Nextcloud Server to version 12.0.3 or later to obtain the security patch. Ensure all user passwords are rotated after applying the update as a precaution, since credentials were compromised in the attack scenario.
Fix this in Nextcloud Server
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-3775 — 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-2018-3775 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
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