Keycloak Redirect URI Wildcard Bypass Leads to Token Theft
CVE-2026-3872 Published on April 2, 2026

Keycloak: keycloak: information disclosure due to redirect_uri validation bypass
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.

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Vulnerability Analysis

CVE-2026-3872 is exploitable with network access, requires user interaction and a small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
REQUIRED
Scope:
UNCHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
NONE

Timeline

Reported to Red Hat.

Made public. 23 days later.

Weakness Type

What is an Open Redirect Vulnerability?

A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks. An http parameter may contain a URL value and could cause the web application to redirect the request to the specified URL. By modifying the URL value to a malicious site, an attacker may successfully launch a phishing scam and steal user credentials. Because the server name in the modified link is identical to the original site, phishing attempts have a more trustworthy appearance.

CVE-2026-3872 has been classified to as an Open Redirect vulnerability or weakness.


Products Associated with CVE-2026-3872

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Affected Versions

Red Hat build of Keycloak 26.2: Red Hat build of Keycloak 26.2: Red Hat build of Keycloak 26.2: Red Hat build of Keycloak 26.2.15: Red Hat build of Keycloak 26.4: Red Hat build of Keycloak 26.4: Red Hat build of Keycloak 26.4: Red Hat build of Keycloak 26.4.11:

Exploit Probability

EPSS
0.03%
Percentile
9.56%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.