What’s Vulnerable › Vulnerabilities

CVE-2026-15565: Undertow: undertow-websockets: undertow: pre-auth dos on websocket endpoint with @serverendpoint class with any @onmessage method

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-11 · updated 2026-11-01
• Weakness: CWE-120

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.

Affected products

• Red Hat build of Apache Camel for Spring Boot 4: all versions
• Red Hat Data Grid 8: all versions
• Red Hat JBoss Enterprise Application Platform 7: all versions
• Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7: all versions — fixed in 0:2.16.0-22.redhat_00057.1.el7eap
• Red Hat JBoss Enterprise Application Platform 8.1.8.GA: all versions — fixed in 2.3.26.SP3-redhat-00001
• Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 10: all versions — fixed in 0:2.40.0-8.redhat_00024.1.el10eap
• Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8: all versions — fixed in 0:2.40.0-8.redhat_00024.1.el8eap
• Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9: all versions — fixed in 0:2.40.0-8.redhat_00024.1.el9eap

How to fix

Upgrade to a fixed version: Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7 0:2.16.0-22.redhat_00057.1.el7eap; Red Hat JBoss Enterprise Application Platform 8.1.8.GA 2.3.26.SP3-redhat-00001; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 10 0:2.40.0-8.redhat_00024.1.el10eap; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 0:2.40.0-8.redhat_00024.1.el8eap; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 0:2.40.0-8.redhat_00024.1.el9eap. Check the vendor advisory for mitigations.

References

• https://access.redhat.com/errata/RHSA-2026:53644
• https://access.redhat.com/errata/RHSA-2026:53806
• https://access.redhat.com/errata/RHSA-2026:70228
• https://access.redhat.com/errata/RHSA-2026:70229
• https://access.redhat.com/errata/RHSA-2026:70230
• https://access.redhat.com/errata/RHSA-2026:70277
• https://access.redhat.com/security/cve/CVE-2026-15565
• https://bugzilla.redhat.com/show_bug.cgi?id=2490628

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