CVE-2026-3872Network attack vector

Access-token theft via semicolon-obscured path traversal

Published Apr 2, 2026 · Updated Apr 2, 2026

Open redirect in Red Hat build of Keycloak 26.2 and 26.4 allows remote authenticated users to steal access tokens through OIDC. RedirectUtils fails to classify a semicolon after a parent-directory segment as unsafe, so a ..;/ sequence passes wildcard redirect path validation. Exploitation requires a wildcard redirect URI, attacker control of another path on the same web server, and user interaction with a crafted authorization request.

CVSS severity7.3
High
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in Red Hat build of Keycloak 26.2 and 26.4 allows remote authenticated users to steal access tokens through OIDC. RedirectUtils fails to classify a semicolon after a parent-directory segment as unsafe, so a ..;/ sequence passes wildcard redirect path validation. Exploitation requires a wildcard redirect URI, attacker control of another path on the same web server, and user interaction with a crafted authorization request.

The record

CVE
CVE-2026-3872
Published
Apr 2, 2026
Updated
Apr 2, 2026
Vendor
389 Directory Server
Product
Red Hat build of Keycloak
Classifications
CWE-601, T1204.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

389 Directory Server · Red Hat build of KeycloakAffected versions are unavailable in this record.

Published CVSS scores

7.3Red Hat Product SecurityCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')
T1204.001User Execution: Malicious Link

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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