This page tracks the Ubuntu fix status. The vulnerability itself is described on the main CVE page.
View CVE-2026-15565 →
UBUNTU-CVE-2026-15565
A flaw was found in Undertow. A remote attacker can cause Out of Memory on websockets endpoint without authentication on any @ServerEndpoint class tha...
Original description
The description as published by the source.
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.
Source: OSV.dev (Open Source Vulnerabilities) OSV
Affected packages
Ubuntu:Pro:16.04:LTS
undertow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:18.04:LTS
undertow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:20.04:LTS
undertow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:22.04:LTS
undertow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:Pro:24.04:LTS
undertow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:26.10
undertow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
Ubuntu:26.04:LTS
undertow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]
References
- report ubuntu.com
- report cve.org
- report bugzilla.redhat.com
- report access.redhat.com
- report access.redhat.com