A flaw was found in Undertow. A remote attacker can cause Out of Memory on websockets endpoint without authentication on any @ServerEndpoint class that has any @OnMessage method. This allows an attacker to cause Denial of Service attack without authentication and using only a standard WebSocket handshake.

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Advisories

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Fixes

Solution

No solution given by the vendor.


Workaround

Option 1 — Server-wide configuration to disable websockets handshake: <!-- Remove <websockets/> from standalone.xml servlet-container --> <servlet-container name="default"> <jsp-config/> <!-- <websockets/> ← remove this line entirely --> </servlet-container> isWebsocketsEnabled() returns false → no WebSocket upgrade accepted for any deployment. Option 2 — Per-application configuration to disable websockets handshake: <!-- WEB-INF/jboss-web.xml inside the WAR --> <jboss-web> <enable-websockets>false</enable-websockets> </jboss-web> Only that specific WAR's @ServerEndpoint classes are not registered.

History

Tue, 11 Aug 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 11 Aug 2026 15:45:00 +0000

Type Values Removed Values Added
First Time appeared Redhat build Of Apache Camel For Spring Boot
Redhat data Grid 8
Redhat fuse
Redhat jboss Enterprise Application Platform Expansion Pack
Redhat single Sign On
Redhat undertow
Vendors & Products Redhat build Of Apache Camel For Spring Boot
Redhat data Grid 8
Redhat fuse
Redhat jboss Enterprise Application Platform Expansion Pack
Redhat single Sign On
Redhat undertow

Tue, 11 Aug 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Important


Tue, 11 Aug 2026 09:15:00 +0000

Type Values Removed Values Added
Description A flaw was found in Undertow. A remote attacker can cause Out of Memory on websockets endpoint without authentication on any @ServerEndpoint class that has any @OnMessage method. This allows an attacker to cause Denial of Service attack without authentication and using only a standard WebSocket handshake.
Title Undertow: undertow-websockets: undertow: pre-auth dos on websocket endpoint with @serverendpoint class with any @onmessage method
First Time appeared Redhat
Redhat camel Spring Boot
Redhat jboss Data Grid
Redhat jboss Enterprise Application Platform
Redhat jboss Fuse
Redhat jbosseapxp
Redhat red Hat Single Sign On
Weaknesses CWE-120
CPEs cpe:/a:redhat:camel_spring_boot:4
cpe:/a:redhat:jboss_data_grid:8
cpe:/a:redhat:jboss_enterprise_application_platform:7
cpe:/a:redhat:jboss_enterprise_application_platform:8
cpe:/a:redhat:jboss_fuse:7
cpe:/a:redhat:jbosseapxp
cpe:/a:redhat:red_hat_single_sign_on:7
Vendors & Products Redhat
Redhat camel Spring Boot
Redhat jboss Data Grid
Redhat jboss Enterprise Application Platform
Redhat jboss Fuse
Redhat jbosseapxp
Redhat red Hat Single Sign On
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-08-11T17:51:04.542Z

Reserved: 2026-07-13T05:42:33.770Z

Link: CVE-2026-15565

cve-icon Vulnrichment

Updated: 2026-08-11T17:48:47.692Z

cve-icon NVD

Status : Received

Published: 2026-08-11T09:17:13.370

Modified: 2026-08-11T18:17:20.980

Link: CVE-2026-15565

cve-icon Redhat

Severity : Important

Publid Date: 2026-08-11T05:55:42Z

Links: CVE-2026-15565 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-11T14:19:48Z

Weaknesses