Louis Dion-Marcil reports:
Due to incorrect pointer handling Squid is vulnerable to denial
of service attack when processing ESI responses.
This problem allows a remote server delivering certain ESI
response syntax to trigger a denial of service for all clients
accessing the Squid service.
Due to unrelated changes Squid-3.5 has become vulnerable to some
regular ESI server responses also triggering this issue.
This problem is limited to the Squid custom ESI parser.
Squid built to use libxml2 or libexpat XML parsers do not have
this problem.
Due to incorrect pointer handling Squid is vulnerable to denial
of service attack when processing ESI responses or downloading
intermediate CA certificates.
This problem allows a remote client delivering certain HTTP
requests in conjunction with certain trusted server responses to
trigger a denial of service for all clients accessing the Squid
service.