A squid security update has been released for CentOS 7.

CESA-2021:1135 Important CentOS 7 squid Security Update

CentOS Errata and Security Advisory 2021:1135 Important

Upstream details at :   https://access.redhat.com/errata/RHSA-2021:1135

The following updated files have been uploaded and are currently
syncing to the mirrors: ( sha256sum Filename )

x86_64:
d71161880783b5c75a2c86c86ecd65a9b1c075f8f6ae57b1c22186db3a0e482b squid-3.5.20-17.el7_9.6.x86_64.rpm
05b86a6126cc85e6e214a09707b886a17df5b705f5cb7dab4c86228f6b2ad4d2 squid-migration-script-3.5.20-17.el7_9.6.x86_64.rpm
147f560470dacac3f89bc4c5cfaa3c9d32364fc302511f2bf1a13025a5875621 squid-sysvinit-3.5.20-17.el7_9.6.x86_64.rpm

Source:
4ef86458d8b6ff61084da478e9df0d5dc69d8fdd2cdfcf9229ce84c82b8b6835 squid-3.5.20-17.el7_9.6.src.rpm