HTTP request smuggling in Undertow

Published: 2021-03-17
Risk Medium
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2021-20220
Exploitation vector Network
Public exploit N/A
Vulnerable software
Server applications / Web servers

Vendor Red Hat Inc.

Security Bulletin

This security bulletin contains one medium risk vulnerability.

1) Inconsistent interpretation of HTTP requests

EUVDB-ID: #VU51518

Risk: Medium


CVE-ID: CVE-2021-20220

CWE-ID: CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling')

Exploit availability: No


The vulnerability allows a remote attacker to preform HTTP request smuggling attacks.

The vulnerability exists due to improper validation of HTTP requests when processing HTTP/1.x and HTTP/2  protocols. A remote attacker can send a specially crafted HTTP request to the server and smuggle arbitrary HTTP headers.

Successful exploitation of vulnerability may allow an attacker to poison HTTP cache and perform phishing attacks.


Install updates from vendor's website.

Vulnerable software versions

Undertow: 2.0.0 - 2.1.5

CPE2.3 External links

Q & A

Can this vulnerability be exploited remotely?

How the attacker can exploit this vulnerability?

Is there known malware, which exploits this vulnerability?