Undertow: undertow: request smuggling via inconsistent header parsing (CVE-2026-28368) | HOL Guard CVE

High · CVSS 8.7CVE-2026-28368GHSA-8V4X-MGVP-P658

Undertow: undertow: request smuggling via inconsistent header parsing

Answer in brief

CVE-2026-28368 records a High severity (CVSS 8.7) vulnerability in Undertow: undertow: request smuggling via inconsistent header parsing. The current sources do not mark it as known exploited. The current feed maps io.undertow:undertow-parent (maven), io.undertow:undertow-parent (maven). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Mar 27, 2026Updated Sep 21, 2026Source checked Sep 21, 2026First seen by HOL Jun 11, 2026Material review Sep 21, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Not reported

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps io.undertow:undertow-parent (maven), io.undertow:undertow-parent (maven). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
io.undertow:undertow-parentmaven	<=2.3.23.Final	Not reported
io.undertow:undertow-parentmaven	>=0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for io.undertow:undertow-parent, io.undertow:undertow-parent.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Mar 27, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Jun 11, 2026

Sources and claim methodology

Upstream source description

A flaw was found in Undertow. This vulnerability allows a remote attacker to construct specially crafted requests where header names are parsed differently by Undertow compared to upstream proxies. This discrepancy in header interpretation can be exploited to launch request smuggling attacks, potentially bypassing security controls and accessing unauthorized resources.

Quoted source text, attributed separately from HOL analysis.