7.5 High

A flaw was found in Undertow.

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 that has any @OnMessage method. This allows an attacker to cause Denial of Service attack without authentication and using only a standard WebSocket handshake.

Assessment

CVSS: 7.5 (v3.1)
Severity: High
EPSS: 1.16% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 11 August 2026
Last updated: 1 November 2026
Affected: Red Hat
Assigner: redhat

CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

At the source

EUVD (ENISA)

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