Undertow is Vulnerable to HTTP Request/Response Smuggling
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.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | io.undertow:undertow-parent | <= 2.3.23.Final | no fix |
References
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N- Weakness (CWE)
CWE-444- Platform
- Java / Kotlin (Maven)
- Package
io.undertow:undertow-parent- Disclosed
- 27.03.2026
- Updated
- 11.10.2026 13:20
Sources and licenses
OSV / GitHub Advisory Database - GHSA-vqqj-9cmv-hx43 - CC BY 4.0
Vulnerability history: io.undertow:undertow-parent
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 4
- First → latest
- 09.2023 03.2026
- Without a fix
- 3
- Exploited in attacks
- 0
Severity breakdown
- High 4
Disclosures per year
- 2023: 1
- 2024: 0
- 2025: 0
- 2026: 3
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Undertow is Vulnerable to HTTP Request/Response Smuggling this entry
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