#VU63634 Inconsistent interpretation of HTTP requests in Puma - CVE-2021-41136

Vulnerability identifier: #VU63634

Vulnerability risk: Medium

CVSSv4.0: 1.2 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-41136

CWE-ID: CWE-444

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Puma
Server applications / Web servers

Vendor: Evan Phoenix

Description

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

The vulnerability exists due to improper validation of HTTP requests. A remote attacker can send a specially crafted HTTP header values which contain the LF character 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

Puma: 4.0.0 - 4.0.1, 4.1.0 - 4.1.1, 4.2.0 - 4.2.1, 4.3.0 - 4.3.12, 5.0.0 - 5.0.4, 5.1.0 - 5.1.1, 5.2.0 - 5.2.2, 5.3.0 - 5.3.2, 5.4.0, 5.5.0

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External links
https://github.com/puma/puma/security/advisories/GHSA-48w2-rm65-62xx
https://github.com/puma/puma/commit/acdc3ae571dfae0e045cf09a295280127db65c7f
https://www.debian.org/security/2022/dsa-5146

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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.