CVE-2020-15811

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.

• CVE ID
• CVE-2020-15811

• Assigner
• cve@mitre.org

• Vulnerability Status
• Analyzed

• Published Version
• 2020-09-02T17:15:11

• Last Modified Date
• 2021-03-04T20:59:03

• Version
• 2.0

• Vector String
• AV:N/AC:L/Au:S/C:N/I:P/A:N

• Access Vector
• NETWORK

• Access Compatibility
• LOW

• Authentication
• SINGLE

• Confidentiality Impact
• NONE

• Integrity Impact
• PARTIAL

• Availability Impact
• NONE

• Base Score
• 4

• Severity
• MEDIUM

• Exploitability Score
• 8

• Impact Score
• 2.9

• Version
• 3.1

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

• Attack Vector
• NETWORK

• Attack Compatibility
• LOW

• Privileges Required
• LOW

• User Interaction
• NONE

• Scope
• UNCHANGED

• Confidentiality Impact
• NONE

• Availability Impact
• NONE

• Base Score
• 6.5

• Base Severity
• MEDIUM

• Exploitability Score
• 2.8

• Impact Score
• 3.6