CVE-2019-12520 Information

Description

An issue was discovered in Squid through 4.7 and 5. When receiving a request Squid checks its cache to see if it can serve up a response. It does this by making a MD5 hash of the absolute URL of the request. If found it servers the request. The absolute URL can include the decoded UserInfo (username and password) for certain protocols. This decoded info is prepended to the domain. This allows an attacker to provide a username that has special characters to delimit the domain and treat the rest of the URL as a path or query string. An attacker could first make a request to their domain using an encoded username then when a request for the target domain comes in that decodes to the exact URL it will serve the attacker’s HTML instead of the real HTML. On Squid servers that also act as reverse proxies this allows an attacker to gain access to features that only reverse proxies can use such as ESI.

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Reference

http://www.squid-cache.org/Versions/v4/ http://www.squid-cache.org/Versions/v4/changesets/ https://github.com/squid-cache/squid/commits/v4 https://gitlab.com/jeriko.one/security/-/blob/master/squid/CVEs/CVE-2019-12520.txt https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html https://usn.ubuntu.com/4446-1/ https://www.debian.org/security/2020/dsa-4682

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

NONE

Base Score

NONE

Base Severity

7.5