HTTP request smuggling in Netty

1) Inconsistent interpretation of HTTP requests

EUVDB-ID: #VU51837

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-2021-21409

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 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.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Netty: 4.0.0 - 4.1.60

External links

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21295
http://github.com/netty/netty/commit/b0fa4d5aab4215f3c22ce6123dd8dd5f38dc0432
http://github.com/netty/netty/security/advisories/GHSA-f256-j965-7f32
http://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj

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.