High [CVE-2026-15565] Pre-Auth DoS on websocket endpoint with @ServerEndpoint class with any @OnMessage method
This high-severity Red Hat Linux advisory covers CVE-2026-15565 affecting Red Hat JBoss Enterprise Application Platform 7.4.25, Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7, Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 8.
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Summary
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. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-120.
Affected Red Hat products: Red Hat JBoss Enterprise Application Platform 7.4.25; Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7; Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 8; Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 9; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 10; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9; Red Hat build of Apache Camel for Spring Boot 4; Red Hat Data Grid 8; Red Hat Fuse 7; Red Hat JBoss Enterprise Application Platform 7; Red Hat Single Sign-On 7.
Red Hat lists Red Hat JBoss Enterprise Application Platform Expansion Pack as not affected. Will not fix / out of support: Red Hat Data Grid 8; Red Hat Fuse 7; Red Hat Single Sign-On 7.
Red Hat fixing advisory: RHSA-2026:53806, RHSA-2026:53644, RHSA-2026:53645, RHSA-2026:53646, RHSA-2026:70230, RHSA-2026:70228, RHSA-2026:70229.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 15 hours ago·verify at source
- io.undertow/undertow-websockets-jsr:2.2.40.SP3-redhat-00001
- eap7-activemq-artemis-0:2.16.0-22.redhat_00057.1.el7eap
- eap7-glassfish-jsf-0:2.3.14-11.SP11_redhat_00001.1.el7eap
- eap7-ironjacamar-0:1.5.26-2.Final_redhat_00001.1.el7eap
- eap7-jackson-annotations-0:2.18.8-1.redhat_00003.1.el7eap
- eap7-jackson-core-0:2.18.8-1.redhat_00003.1.el7eap
- eap7-jackson-databind-0:2.18.8-1.redhat_00003.1.el7eap
- eap7-jackson-jaxrs-providers-0:2.18.8-1.redhat_00003.1.el7eap
- eap7-jackson-modules-base-0:2.18.8-1.redhat_00003.1.el7eap
- eap7-jackson-modules-java8-0:2.18.8-1.redhat_00003.1.el7eap
- eap7-jboss-remoting-0:5.0.31-3.SP2_redhat_00001.1.el7eap
- eap7-jboss-server-migration-0:1.10.0-46.Final_redhat_00044.1.el7eap
- eap7-netty-0:4.1.135-1.Final_redhat_00001.1.el7eap
- eap7-netty-transport-native-epoll-0:4.1.135-1.Final_redhat_00001.1.el7eap
- eap7-picketlink-bindings-0:2.5.5-30.SP12_redhat_00020.1.el7eap
- eap7-picketlink-federation-0:2.5.5-24.SP12_redhat_00016.1.el7eap
- eap7-undertow-0:2.2.40-2.SP3_redhat_00001.1.el7eap
- eap7-wildfly-0:7.4.25-2.GA_redhat_00001.1.el7eap
- eap7-activemq-artemis-0:2.16.0-22.redhat_00057.1.el8eap
- eap7-glassfish-jsf-0:2.3.14-11.SP11_redhat_00001.1.el8eap
- eap7-ironjacamar-0:1.5.26-2.Final_redhat_00001.1.el8eap
- eap7-jackson-annotations-0:2.18.8-1.redhat_00003.1.el8eap
- eap7-jackson-core-0:2.18.8-1.redhat_00003.1.el8eap
- eap7-jackson-databind-0:2.18.8-1.redhat_00003.1.el8eap
- eap7-jackson-jaxrs-providers-0:2.18.8-1.redhat_00003.1.el8eap
- eap7-jackson-modules-base-0:2.18.8-1.redhat_00003.1.el8eap
- eap7-jackson-modules-java8-0:2.18.8-1.redhat_00003.1.el8eap
- eap7-jboss-remoting-0:5.0.31-3.SP2_redhat_00001.1.el8eap
- eap7-jboss-server-migration-0:1.10.0-46.Final_redhat_00044.1.el8eap
- eap7-netty-0:4.1.135-1.Final_redhat_00001.1.el8eap
- eap7-netty-transport-native-epoll-0:4.1.135-1.Final_redhat_00001.1.el8eap
- eap7-picketlink-bindings-0:2.5.5-30.SP12_redhat_00020.1.el8eap
- eap7-picketlink-federation-0:2.5.5-24.SP12_redhat_00016.1.el8eap
- eap7-undertow-0:2.2.40-1.SP3_redhat_00001.1.el8eap
- eap7-wildfly-0:7.4.25-2.GA_redhat_00001.1.el8eap
- eap7-activemq-artemis-0:2.16.0-22.redhat_00057.1.el9eap
- eap7-glassfish-jsf-0:2.3.14-11.SP11_redhat_00001.1.el9eap
- eap7-ironjacamar-0:1.5.26-2.Final_redhat_00001.1.el9eap
- eap7-jackson-annotations-0:2.18.8-1.redhat_00003.1.el9eap
- eap7-jackson-core-0:2.18.8-1.redhat_00003.1.el9eap
- RHSA-2026:53806
- RHSA-2026:53644
- RHSA-2026:53645
- RHSA-2026:53646
- RHSA-2026:70230
- RHSA-2026:70228
- RHSA-2026:70229
Official advisory · high-confidence parse· fetched 15 hours ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 15 hours ago·verify at source
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