VulnerabilityPublished 28 May 2026Updated 26 Jun 2026

CVE-2026-9801: Red Hat build of Keycloak 26.4 · Improper Validation of Specified Quantity in Input

Affects Red Hat build of Keycloak 26.4Source CVE Database V5

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Not known to be exploited · CVSS 4.9 Medium.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

4.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: High
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Red HatRed Hat build of Keycloak 26.4	Affected–	Fixed in–
Red HatRed Hat build of Keycloak 26.4	Affected–	Fixed in–
Red HatRed Hat build of Keycloak 26.4.13	Affected–	Fixed in–
Red HatRed Hat build of Keycloak 26.6	Affected–	Fixed in–
Red HatRed Hat build of Keycloak 26.6	Affected–	Fixed in–
Red HatRed Hat build of Keycloak 26.6.3	Affected–	Fixed in–

AI-suggested

Red Hat has released updated Red Hat build of Keycloak 26.6.3 images that include fixes for CVE-2026-9801. Users should update to these new images as provided in the Red Hat advisories RHSA-2026:25097 and RHSA-2026:25098. Before applying updates, back up existing installations including applications, configuration files, and databases. No other specific mitigations or temporary workarounds are mentioned in the vendor advisory.

Description

A flaw was found in Keycloak. A remote attacker with high privileges, such as a realm administrator configuring a malicious Lightweight Directory Access Protocol (LDAP) server or an attacker compromising an upstream LDAP server, could exploit this vulnerability. By sending a malformed LDAP password policy response during a password authentication request, the attacker can trigger an OutOfMemoryError. This causes the Keycloak Java Virtual Machine (JVM) to terminate, leading to a denial of service (DoS) for all realms on the affected node.

Impact

Successful exploitation results in a denial of service (DoS) condition by causing the Keycloak JVM to terminate due to an OutOfMemoryError. This disrupts authentication services for all realms on the affected node. There is no impact on confidentiality or integrity reported. The attacker must have high privileges such as a realm administrator or control over an upstream LDAP server to exploit this vulnerability.

Summary

The vulnerability CVE-2026-9801 affects Red Hat build of Keycloak 26.4 and allows a remote attacker with high privileges to cause a denial of service by sending a malformed LDAP password policy response during authentication. This malformed response triggers an OutOfMemoryError in the Keycloak JVM, causing it to terminate and resulting in service disruption for all realms on the affected node. The issue arises from improper validation of specified quantity in input. Red Hat has published security advisories (RHSA-2026:25097 and RHSA-2026:25098) releasing new Keycloak 26.6.3 images that address this and other vulnerabilities. The advisories recommend updating to these new images to mitigate the issue. However, the advisories do not explicitly state a patch or fix specifically for CVE-2026-9801 outside of the new image releases.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Jun 2026, 12:22 UTC

Technical details

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