CVE-2026-18206Network attack vector

Unauthenticated client modification via wildcard suffix matching

Published Jul 31, 2026 · Updated Jul 31, 2026

Improper input validation in Red Hat build of Keycloak allows remote attackers to bypass source-host client policy restrictions. The keycloak-services wildcard matcher accepts any reverse-resolved hostname ending in the configured domain suffix without enforcing a label boundary. Exploitation requires a realm administrator to configure a wildcard source-host policy and an unauthenticated attacker to control reverse DNS, enabling unauthorized client registration or updates but no reported data disclosure or service interruption.

CVSS severity3.7
Low
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Red Hat build of Keycloak allows remote attackers to bypass source-host client policy restrictions. The keycloak-services wildcard matcher accepts any reverse-resolved hostname ending in the configured domain suffix without enforcing a label boundary. Exploitation requires a realm administrator to configure a wildcard source-host policy and an unauthenticated attacker to control reverse DNS, enabling unauthorized client registration or updates but no reported data disclosure or service interruption.

The record

CVE
CVE-2026-18206
Published
Jul 31, 2026
Updated
Jul 31, 2026
Vendor
389 Directory Server
Product
Red Hat build of Keycloak
Classifications
CWE-20, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 31, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 31, 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 privilegesunauthenticated

What is affected?

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

Published CVSS scores

3.7Red HatCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

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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