Vulnerability identifier: #VU51836

Vulnerability 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

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Netty
Universal components / Libraries / Libraries used by multiple products

Vendor: 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 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

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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
http://lists.apache.org/thread.html/r02e467123d45006a1dda20a38349e9c74c3a4b53e2e07be0939ecb3f@%3Cdev.ranger.apache.org%3E
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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.