CVE-2026-5680: Undertow-core: undertow: denial of service via websocket permessage-deflate processing

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-27 · updated 2026-10-20
Weakness: CWE-770

Description

A flaw was found in Undertow. A remote attacker could exploit this vulnerability by sending specially crafted WebSocket messages with permessage-deflate negotiated. This could lead to excessive memory consumption due to the PerMessageDeflateFunction.largerBuffer() method using exponential doubling, resulting in a Denial of Service (DoS) for the affected application.

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 8: all versions
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 0:1.1.9-1.redhat_00001.1.el10eap, 0:1.2.7-1.redhat_00002.1.el10eap, 0:1.85.0-1.redhat_00001.1.el10eap, 0:2.0.18-1.redhat_00001.1.el10eap, 0:2.0.5-1.Final_redhat_00001.1.el10eap, 0:2.1.0-1.redhat_00001.1.el10eap
Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8: all versions — fixed in 0:1.1.9-1.redhat_00001.1.el8eap, 0:1.2.7-1.redhat_00002.1.el8eap, 0:1.85.0-1.redhat_00001.1.el8eap, 0:2.0.18-1.redhat_00001.1.el8eap, 0:2.0.5-1.Final_redhat_00001.1.el8eap, 0:2.1.0-1.redhat_00001.1.el8eap
Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9: all versions — fixed in 0:1.1.9-1.redhat_00001.1.el9eap, 0:1.2.7-1.redhat_00002.1.el9eap, 0:1.85.0-1.redhat_00001.1.el9eap, 0:2.0.18-1.redhat_00001.1.el9eap, 0:2.0.5-1.Final_redhat_00001.1.el9eap, 0:2.1.0-1.redhat_00001.1.el9eap
Red Hat JBoss Enterprise Application Platform Expansion Pack: all versions
Red Hat Process Automation 7: all versions
Red Hat Single Sign-On 7: all versions

How to fix

Upgrade to a fixed version: 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 0:1.1.9-1.redhat_00001.1.el10eap, 0:1.2.7-1.redhat_00002.1.el10eap, 0:1.85.0-1.redhat_00001.1.el10eap, 0:2.0.18-1.redhat_00001.1.el10eap; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 8 0:1.1.9-1.redhat_00001.1.el8eap, 0:1.2.7-1.redhat_00002.1.el8eap, 0:1.85.0-1.redhat_00001.1.el8eap, 0:2.0.18-1.redhat_00001.1.el8eap; Red Hat JBoss Enterprise Application Platform 8.1 for RHEL 9 0:1.1.9-1.redhat_00001.1.el9eap, 0:1.2.7-1.redhat_00002.1.el9eap, 0:1.85.0-1.redhat_00001.1.el9eap, 0:2.0.18-1.redhat_00001.1.el9eap. Check the vendor advisory for mitigations.

References

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