CVE-2026-28367

undertow: Undertow: Request smuggling via `\r\r\r` as a header block terminator

Published 27 Mar 2026Modified 26 Oct 2026CWE 444

In the Trivy database since at least 24 Oct 2026, 07:11 UTCWhen it arrived before that build is not recorded.

Severity by source

NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

GHSA8.7CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

Red Hat8.7CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

Trivy's own label is CRITICAL. Rated critical by NVD. Rated lower by GHSA (high), Red Hat (high).

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.

Affected packages and fixed versions

Source	Package	Fixed in
debian 14	undertow	no fix listed
maven::GitHub Security Advisory Maven	io.undertow:undertow-parent	no fix listed
Red Hat	undertow-core	no fix listed

References

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Vulnerability data compiled from the Trivy vulnerability database (trivy-db, Aqua Security, Apache License 2.0), which aggregates third-party advisories. CVE records are published by The MITRE Corporation under the CVE Terms of Use; CVE is a trademark of MITRE. This product uses data from the NVD API but is not endorsed or certified by the NVD. Severity, titles and advisory data from the GitHub Advisory Database (CC BY 4.0), Red Hat security data (CC BY 4.0) and the other sources linked on each entry. Entries may be summarised or re-formatted; the linked original is the authoritative record.