#VU51837 Inconsistent interpretation of HTTP requests in Netty - CVE-2021-21409
Published: April 1, 2021 / Updated: February 11, 2025
Vulnerability identifier: #VU51837
Vulnerability risk: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2021-21409
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Netty
Netty
Software vendor:
Netty project
Netty project
Description
The vulnerability allows a remote attacker to preform HTTP request smuggling attacks.
The vulnerability exists due to improper validation of HTTP requests in io.netty:netty-codec-http2 in Netty, if the request only uses a single Http2HeaderFrame with the endStream set to to true. 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.
Remediation
Install updates from vendor's website.