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Build Of KeycloakApplication · Redhat

CVE-2026-3872

HIGH · 7.3 CVSS v3.1 Published 2026-04-02
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
77/100
Remediation priority · High
Remotely reachable

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. This issue allows an attacker, who controls another path on the same web server, to bypass the allowed path in redirect Uniform Resource Identifiers (URIs) that use a wildcard. A successful attack may lead to the theft of an access token, resulting in information disclosure.

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 · moderate confidence

Keycloak's redirect URI validation for wildcard paths can be bypassed when an attacker controls an alternative path on the same web server. By crafting a malicious redirect URI that exploits the wildcard matching logic, an attacker can intercept the authorization code or access token intended for a legitimate client, leading to token theft and unauthorized access to user resources.

MitigationUpgrade Keycloak to the version that patches this vulnerability. Additionally, review and restrict redirect URIs to exact matches rather than wildcards wherever possible, and ensure no untrusted paths exist on the same web server infrastructure.

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
Build Of KeycloakApplication
Affected:all versions= 26.2= 26.2.15= 26.4= 26.4.11

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
Low
Privileges
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/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 version
    Check the running Keycloak instance version by querying the server's admin console, startup logs, or running 'kc.sh show-version' (or 'kc.bat show-version' on Windows) from the Keycloak bin directory.
    Affected if The installed version matches 26.2, 26.2.15, 26.4, 26.4.11, or any version of the Red Hat Build of Keycloak (noting the 'all versions' designation in the affected products).
  2. Locate client configurations with wildcard redirect URIs
    In the Keycloak admin console, navigate to each realm and inspect Clients > Client ID > Settings > Valid Redirect URIs. Look for redirect URI patterns containing asterisks (*) such as 'https://example.com/*' or 'http://localhost:8080/*'. Alternatively, query the Keycloak database (COMPONENT table in realm schema) for entries where PROVIDER_ID contains 'redirect' and VALUE contains wildcard patterns.
    Affected if Any client registered in Keycloak has a Valid Redirect URI configured with a wildcard pattern (contains *).
  3. Audit for untrusted paths on the web server
    Review the web server (e.g., Apache, Nginx, or the application server hosting Keycloak) configuration to enumerate all deployed applications, virtual hosts, or path mappings. Check for any applications or endpoints that allow user-controlled content or are accessible to untrusted users on the same domain or subdomain used in the wildcard redirect URI.
    Affected if There exists an alternate path, application, or subdomain on the same web server infrastructure that an attacker could control or that accepts user-supplied content, and this aligns with the domain pattern in a wildcard redirect URI.

A user is affected if their Keycloak installation is any version of the Red Hat Build of Keycloak or versions 26.2/26.2.15/26.4/26.4.11, AND they have clients configured with wildcard redirect URIs, AND there is an attacker-controllable path on the same web server matching that wildcard pattern.

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

Upgrade Keycloak to the version that patches this vulnerability. Additionally, review and restrict redirect URIs to exact matches rather than wildcards wherever possible, and ensure no untrusted paths exist on the same web server infrastructure.

Fix this in Build Of Keycloak Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2026-3872 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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