Undertow is Vulnerable to HTTP Request/Response Smuggling (CVE-2026-28369) | HOL Guard CVE

High · CVSS 8.7CVE-2026-28369GHSA-VQQJ-9CMV-HX43

Undertow is Vulnerable to HTTP Request/Response Smuggling

Answer in brief

CVE-2026-28369 records a High severity (CVSS 8.7) vulnerability in Undertow is Vulnerable to HTTP Request/Response Smuggling. 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 10, 2026Source checked Sep 17, 2026First seen by HOL Jun 11, 2026Material review Sep 10, 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:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv: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. 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.

Quoted source text, attributed separately from HOL analysis.