CVE-2026-81624
Undertow-core: undertow: websocketcontainer defaults for buffers and timeouts are infinite
What happened?
Undertow is a flexible performant web server used in JBoss EAP and WildFly. A flaw was found in how Undertow handles WebSocket connections. Specifically, certain configuration limits like message buffer sizes and session timeouts cannot be adjusted and default to being unlimited. This allows a remote attacker to send large amounts of data or maintain connections indefinitely, potentially crashing the server by exhausting its memory or other resources.
Affected software and versions
| Software | Version information | Fixed version |
|---|---|---|
| undertow-coreRed Hat | Default status: affected | See vendor advisory |
| moditectRed Hat | Default status: unaffected | See vendor advisory |
| pki-core:10.6/resteasyRed Hat | Default status: unaffected | See vendor advisory |
| pki-deps:10.6/resteasyRed Hat | Default status: unaffected | See vendor advisory |
| resteasyRed Hat | Default status: unaffected | See vendor advisory |
| undertow-coreRed Hat | Default status: affected | See vendor advisory |
| jboss-eap-7/eap74-els-openjdk11-openshift-rhel8Red Hat | Default status: affected | See vendor advisory |
| jboss-eap-7/eap74-els-openjdk17-openshift-rhel8Red Hat | Default status: affected | See vendor advisory |
| jboss-eap-7/eap74-els-openjdk8-openshift-rhel8Red Hat | Default status: affected | See vendor advisory |
| undertow-coreRed Hat | Default status: affected | See vendor advisory |
| undertow-coreRed Hat | Default status: affected | See vendor advisory |
| undertow-coreRed Hat | Default status: unaffected | See vendor advisory |
| undertow-coreRed Hat | Default status: affected | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.