#VU56106 Improper Authorization in envoy - CVE-2021-32777

Vulnerability identifier: #VU56106

Vulnerability risk: Medium

CVSSv4.0: 2.7 [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-2021-32777

CWE-ID: CWE-285

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
envoy
Server applications / IDS/IPS systems, Firewalls and proxy servers

Vendor: Cloud Native Computing Foundation

Description

The vulnerability allows a remote attacker to bypass authorization process.

The vulnerability exists due to an error in ext-authz extension when sending request headers to the external authorization service in Envoy. The application sends only the last header instead of merging multiple value headers according to the HTTP specification. A remote attacker can bypass authorization process and gain unauthorized access to the application, if ext-authz extension is used.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

envoy: 1.16.0 - 1.19.0

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External links
https://github.com/envoyproxy/envoy/security/advisories/GHSA-6g4j-5vrw-2m8h
https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history

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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.