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Improper Certificate ValidationWeakness · CWE-295

CVE-2019-25652

HIGH · 7.5 CVSS v3.1 Published 2026-03-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
No privileges 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
UniFi Network Controller before version 5.10.22 and 5.11.x before 5.11.18 contains an improper certificate verification vulnerability that allows adjacent network attackers to conduct man-in-the-middle attacks by presenting a false SSL certificate during SMTP connections. Attackers can intercept SMTP traffic and obtain credentials by exploiting the insecure SSL host verification mechanism in the SMTP certificate validation process.

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

The UniFi Network Controller versions prior to 5.10.22 and 5.11.x before 5.11.18 fail to properly verify SSL certificates during SMTP connections. The SSL host verification mechanism is insecure, allowing attackers on the adjacent network to present a fraudulent certificate and intercept SMTP traffic to obtain credentials via man-in-the-middle attacks.

MitigationUpgrade UniFi Network Controller to version 5.10.22 or 5.11.18 or later to patch the improper certificate verification vulnerability. If immediate upgrade is not possible, restrict network access to the SMTP server and avoid using untrusted networks.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
Adjacent
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:A/AC:H/PR:N/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify UniFi Network Controller version
    Log into the UniFi Controller web interface and navigate to Settings > System > About, or check the controller's welcome page. Alternatively, check the installation directory or changelog for the version number.
    Affected if The installed version is earlier than 5.10.22, or is 5.11.x earlier than 5.11.18.
  2. Confirm SMTP is configured
    In the UniFi Controller, go to Settings > Notifications > Email Settings (or similar SMTP configuration section). Verify that an SMTP server is configured and enabled for sending email alerts.
    Affected if SMTP is configured and the controller sends email notifications.
  3. Verify SSL/TLS is enabled for SMTP
    In the SMTP configuration settings, check whether SSL or TLS encryption is enabled for the outgoing mail connection.
    Affected if SSL or TLS is enabled for SMTP (the vulnerability only applies when encryption is used but verification is broken).

You are affected if your UniFi Controller version is below 5.10.22 or below 5.11.18, and you have SMTP with SSL/TLS configured for email notifications.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade UniFi Network Controller to version 5.10.22 or 5.11.18 or later to patch the improper certificate verification vulnerability. If immediate upgrade is not possible, restrict network access to the SMTP server and avoid using untrusted networks.

Recommended fix Moderate confidence

UniFi Network Controller 5.10.22 or later, or 5.11.18 or later

  1. 1. Identify the current UniFi Network Controller version by accessing the controller web interface or checking the system information.
  2. 2. Create a full backup of the UniFi configuration through the controller settings (Settings > Maintenance > Backup).
  3. 3. Download the fixed UniFi Network Controller version (5.10.22 or later for the 5.10.x branch, or 5.11.18 or later for the 5.11.x branch) from the official Ubiquiti Downloads page.
  4. 4. Stop the UniFi Controller service before upgrading.
  5. 5. Install the updated UniFi Network Controller package using the appropriate method for your deployment (Docker, Linux package, or Windows installer).
  6. 6. Start the UniFi Controller service and verify it runs without errors.
  7. 7. Confirm the installed version matches the fixed release (5.10.22+ or 5.11.18+) through the controller web interface.
  8. 8. Test SMTP functionality to verify the certificate validation fix is working correctly.
Caveat Review Ubiquiti release notes for any configuration changes between your current version and the target fixed version before upgrading

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

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,120
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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-2019-25652 in production — separate from our analysis above.

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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
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  • No spam, self-promotion, credentials, or personal data