Squid security advisory 2016:1 reports:
Due to incorrectly handling server errors Squid is vulnerable to a denial of service attack when connecting to TLS or SSL servers. This problem allows any trusted client to perform a denial of service attack on the Squid service regardless of whether TLS or SSL is configured for use in the proxy. Misconfigured client or server software may trigger this issue to perform a denial of service unintentionally. However, the bug is exploitable only if Squid is built using the --with-openssl option.
The FreeBSD port does not use SSL by default and is not vulnerable in the default configuration.