HTTP request smuggling in Netty

1) Inconsistent interpretation of HTTP requests

EUVDB-ID: #VU51836

Risk: Medium

CVSSv3.1: 6.3 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-21295

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

Exploit availability: No

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 when converting HTTP/2 to HTTP/1 streams. 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.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Netty: 4.0.0 - 4.1.59

External links

http://github.com/Netflix/zuul/pull/980
http://github.com/netty/netty/commit/89c241e3b1795ff257af4ad6eadc616cb2fb3dc4
http://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj
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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.