Undertow is Vulnerable to HTTP Request/Response Smuggling
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 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-3gv6-g396-9v4r - 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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