#VU53020 Input validation error in Squid - CVE-2021-31806

Vulnerability identifier: #VU53020

Vulnerability risk: Medium

CVSSv4.0: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:A/U:Green]

CVE-ID: CVE-2021-31806

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: Yes

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

Vendor: Squid-cache.org

Description

The vulnerability allows a remote client to perform a denial of service (DoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input when performing HTTP Range requests. A remote proxy client can send specially crafted HTTP request via the proxy server  and perform a denial of service (DoS) attack.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Squid: 2.5_.stable1 - 2.5.9, 2.7.stable1 - 2.7, 3.0.stable1 - 3.5.28, 4.0 - 4.14, 5.0 - 5.0.5

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External links
https://github.com/squid-cache/squid/security/advisories/GHSA-pxwq-f3qr-w2xf/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, a fully functional exploit for this vulnerability is available.