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CVE-2026-15565 – Pre-Authentication Denial of Service (WebSocket Out of Memory) – Red Hat Undertow

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Summary

CVE-2026-15565 is a pre-authentication denial-of-service vulnerability in Red Hat Undertow’s WebSocket implementation. An unauthenticated remote attacker can cause an Out of Memory condition against any @ServerEndpoint class that defines an @OnMessage method, resulting in service unavailability. Red Hat rates the flaw as Important with a CVSS v3.1 base score of 7.5 (High).

Technical details

  • Root cause: Improper memory handling in Undertow’s WebSocket message processing (CWE-120, Buffer Copy without Checking Size of Input), affecting endpoints annotated with @ServerEndpoint and containing an @OnMessage method.
  • Trigger conditions: An attacker interacts with an affected WebSocket endpoint via a standard WebSocket handshake; no authentication, privileges, or user interaction are required.
  • Attack vector: Network (remote, unauthenticated).
  • Impact: Memory exhaustion (Out of Memory) leading to denial of service. There is no impact to confidentiality or integrity; the impact is limited to availability.

Affected software

  • Red Hat build of Apache Camel for Spring Boot 4
  • Red Hat Data Grid 8
  • Red Hat JBoss Enterprise Application Platform 7 and 8
  • Red Hat Fuse 7
  • Red Hat Single Sign-On 7

Severity

  • CVSS v3.1 base score: 7.5 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Mitigation and recommended actions

  • Immediate: Apply the fixed packages published by Red Hat for the affected products as they become available; consult the Red Hat security advisory for per-product update status.
  • If no patch is available, workarounds:
    • Disable WebSockets server-wide by removing <websockets/> from the servlet-container configuration in standalone.xml.
    • Disable WebSockets per-application by adding <enable-websockets>false</enable-websockets> to WEB-INF/jboss-web.xml.

References

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