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KeycloakApplication · Redhat

CVE-2020-1758

MEDIUM · 5.9 CVSS v3.1 Published 2020-05-15
Fix available
A fix is available. Upgrade to 10.0.0 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable 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
A flaw was found in Keycloak in versions before 10.0.0, where it does not perform the TLS hostname verification while sending emails using the SMTP server. This flaw allows an attacker to perform a man-in-the-middle (MITM) 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 confidence

Keycloak before version 10.0.0 fails to perform TLS hostname verification when connecting to SMTP servers for email sending. During the TLS handshake, Keycloak does not validate that the certificate presented by the SMTP server matches the expected hostname, enabling a man-in-the-middle attacker to intercept or modify email traffic.

MitigationUpgrade Keycloak to version 10.0.0 or later which implements proper TLS hostname verification for SMTP connections.

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
KeycloakApplication
Affected:< 10.0.0
OpenstackApplication
Affected:= 10

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

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

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

  1. Identify Keycloak installation and version
    Check the Keycloak version by inspecting the product manifest or startup logs. Common locations: $KEYCLOAK_HOME/bin/product.conf, the JAR manifest, or the server startup log (search for 'Keycloak' or 'WildFly' version info). RPM-based systems can also use: rpm -qi keycloak
    Affected if The installed Keycloak version is below 10.0.0 (e.g., 9.x, 8.x, 7.x)
  2. Determine if SMTP email sending is configured
    Locate the Keycloak configuration file (typically standalone.xml, standalone-ha.xml, or domain.xml in the configuration directory). Search for the <spi name="email"> section or the <handlers> section containing SMTP settings. In the admin console, check Realm Settings -> Email.
    Affected if SMTP server settings are defined and email sending is enabled in the Keycloak configuration
  3. Verify SMTP TLS/SSL transport configuration
    In the email configuration section of standalone.xml (under <spi name="email">), examine the <properties> element for properties such as 'ssl', 'starttls', or 'trustStore'. Check if the SMTP connection uses SSL/TLS transport.
    Affected if SMTP is configured with SSL or STARTTLS enabled, but the Keycloak version is vulnerable (pre-10.0.0)
  4. Confirm hostname verification is not enforced
    Review the SMTP configuration properties for any explicit hostname verification settings. In pre-10.0.0 versions, there is no option to enable strict hostname verification - it is simply missing or disabled by default.
    Affected if The configuration lacks proper hostname verification (this is the default vulnerable state in versions < 10.0.0)

You are affected if you run Keycloak version below 10.0.0 and have SMTP/email sending configured with TLS/SSL enabled, as the TLS hostname verification is not performed during SMTP connections.

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.

From vendor data
Upgrade available Upgrade to 10.0.0 or later
Fixed in 10.0.0
Interim mitigation

Upgrade Keycloak to version 10.0.0 or later which implements proper TLS hostname verification for SMTP connections.

Fix this in Keycloak Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

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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-2020-1758 in production — separate from our analysis above.

No notes yet

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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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data