Rule Category

SERVER-WEBAPP -- Snort has detected traffic exploiting vulnerabilities in web based applications on servers.

Alert Message

SERVER-WEBAPP Squid host header cache poisoning attempt

Rule Explanation

This event is generated when a request has been made to Squid proxy which returns cache content from somewhere other than hostname specified in absolute URI from request line Impact: Results in future requests made to poisoned hostname to return content not originating from hostname Details: Ease of Attack: Simple

What To Look For

Known Usage

No public information

False Positives

No known false positives


Cisco Talos Intelligence Group

MITRE ATT&CK Framework



For reference, see the MITRE ATT&CK vulnerability types here:


Additional Links

Rule Vulnerability

CVE Additional Information

CVE-2016-4553 in Squid before 3.5.18 and 4.x before 4.0.10 does not properly ignore the Host header when absolute-URI is provided, which allows remote attackers to conduct cache-poisoning attacks via an HTTP request.
Severity Base Score8.6
Impact Score4.0 Exploit Score3.9
Confidentiality ImpactNONE Integrity ImpactHIGH
Availability ImpactNONE Access Vector
Authentication Ease of Access