MailApplication · Nextcloud
CVE-2020-8156
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 · uneditedA missing verification of the TLS host in Nextcloud Mail 1.1.3 allowed a man in the middle attack.
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 confidenceNextcloud Mail version 1.1.3 fails to verify the TLS host during secure connections, allowing an attacker positioned between the client and server to intercept encrypted traffic by presenting a fraudulent certificate. This is a classic certificate/hostname validation bypass in the mail client's IMAP or SMTP connection handling.
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
MailApplication
< 1.1.4
FedoraOperating system
= 32CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:L
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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Check Nextcloud Mail app versionNavigate to Nextcloud admin panel or app store, or inspect the app metadata file (appinfo/info.xml) in the Nextcloud installation directory under /apps/mail/ to find the installed version number.Affected if The installed version is 1.1.3 or any version earlier than 1.1.4 (e.g., 1.1.0, 1.0.x, etc.)
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Identify configured mail accountsCheck the Nextcloud database or user settings to see if any IMAP or SMTP accounts are configured in the Mail app. This can be done by querying the oc_mail_accounts table or viewing individual user mail settings through the web interface.Affected if IMAP or SMTP accounts are configured and active, because the TLS verification flaw only applies when the mail client attempts to establish secure connections to mail servers.
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Verify mail transport configurationInspect the Mail app settings or configuration files to confirm whether accounts are using IMAPS (port 993) or SMTP with TLS/SSL enabled, as opposed to unencrypted connections.Affected if Accounts are configured to use secure/encrypted connections (IMAPS on 993, SMTPS on 465, or STARTTLS on 587/25) since the vulnerability specifically bypasses TLS host verification for encrypted transports.
A user is affected if they have Nextcloud Mail version 1.1.3 or earlier installed and have configured IMAP/SMTP accounts using encrypted connections.
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 data1.1.4
Upgrade Nextcloud Mail to version 1.1.4 or later which includes proper TLS host verification. If unable to upgrade immediately, avoid using untrusted networks.
Fix this in Mail
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-2020-8156 — 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-2020-8156 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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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.
- 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