CVE-2026-9801Network attack vector

Node-wide denial of service via oversized BER length

Published May 28, 2026 · Updated May 28, 2026

Improper input validation in Red Hat build of Keycloak 26.4 and 26.6 allows remote authenticated users to terminate an affected node. The LDAP federation BER decoder accepts a length value larger than the remaining PasswordPolicyControl buffer and attempts an oversized array allocation, causing an OutOfMemoryError. Exploitation requires a configured LDAP user-storage provider and control of its server or realm-administrator access; termination interrupts every realm on that node.

CVSS severity4.9
Medium
EPSS probability0.48%
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 26.4 and 26.6 allows remote authenticated users to terminate an affected node. The LDAP federation BER decoder accepts a length value larger than the remaining PasswordPolicyControl buffer and attempts an oversized array allocation, causing an OutOfMemoryError. Exploitation requires a configured LDAP user-storage provider and control of its server or realm-administrator access; termination interrupts every realm on that node.

The record

CVE
CVE-2026-9801
Published
May 28, 2026
Updated
May 28, 2026
Vendor
389 Directory Server
Product
Red Hat build of Keycloak
Classifications
CWE-1284, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 28, 2026CVE publishedPublication date reported by the CVE source.
  2. May 28, 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

4.9Red Hat, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

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-1284Improper Validation of Specified Quantity in Input
T1499Endpoint Denial of Service

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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