Squid upstream has released a security advisory for Squid, covering the DoS issue in the HTCP protocol handler:
Due to incorrect processing Squid is vulnerable to a denial of
service attack when receiving specially crafted HTCP packets.
Specially-crafted HTCP packet may cause squid child process to crash (NULL pointer dereference), resulting in a temporary DoS as new child process is started by the squid parent process.
Upstream patches (2.x and 3.x):
This issue did not affect squid packages as shipped in Red Hat Enterprise Linux 3, 4 and 5, as they do not have support for HTCP enabled (it is disabled by default in 2.5 and 2.6 versions and is not enabled explicitly in RHEL builds). Newer squid versions enable HTCP by default.
squid-18.104.22.168-6.fc12 has been submitted as an update for Fedora 12.
squid-22.214.171.124-7.fc13 has been submitted as an update for Fedora 13.
squid-126.96.36.199-7.fc13 has been pushed to the Fedora 13 stable repository. If problems still persist, please make note of it in this bug report.
squid-188.8.131.52-6.fc12 has been pushed to the Fedora 12 stable repository. If problems still persist, please make note of it in this bug report.
squid-3.0.STABLE24-1.fc11 has been pushed to the Fedora 11 stable repository. If problems still persist, please make note of it in this bug report.