Incorrect processing of responses to If-None-Modified HTTP conditional requests in Squid HTTP Proxy 3.1.10 through 3.1.23, 3.2.0.3 through 3.5.22, and 4.0.1 through 4.0.16 leads to client-specific Cookie data being leaked to other clients. Attack requests can easily be crafted by a client to probe a cache for this information.

client_side_request.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via crafted Edge Side Includes (ESI) responses.

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

client_side.cc 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.