Due to improper input validation Squid is vulnerable to an HTTP
Request Smuggling attack.

Severity:

This problem allows a trusted client to perform HTTP Request
Smuggling and access services otherwise forbidden by Squid
security controls.

CVSS Score of 9.3
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N/E:F/RL:O/RC:C/CR:H/IR:X/AR:X/MAV:N/MAC:L/MPR:N/MUI:N/MS:C/MC:H/MI:X/MA:X&version=3.1

Updated Packages:

This bug is fixed by Squid versions 4.14 and 5.0.5.

In addition, patches addressing this problem for the stable
releases can be found in our patch archives:

Squid 4:

http://www.squid-cache.org/Versions/v4/SQUID-2020_11.patch

If you are using a prepackaged version of Squid then please refer
to the package vendor for availability information on updated
packages.

Determining if your version is vulnerable:

All Squid with squid.conf containing "uri_whitespace deny" are
not vulnerable.

All Squid with squid.conf containing "uri_whitespace encode" are
not vulnerable.

All Squid-4.x up to and including 4.13 without uri_whitespace in
squid.conf are vulnerable.

All Squid-4.x up to and including 4.13 with uri_whitespace in
squid.conf configured to "allow" are vulnerable.

All Squid-4.x up to and including 4.13 with uri_whitespace in
squid.conf configured to "chop" are vulnerable.

All Squid-4.x up to and including 4.13 with uri_whitespace in
squid.conf configured to "strip" are vulnerable.

All Squid-5.x up to and including 5.0.4 without uri_whitespace
in squid.conf are vulnerable.

All Squid-5.x up to and including 5.0.4 with uri_whitespace in
squid.conf configured to "allow" are vulnerable.

All Squid-5.x up to and including 5.0.4 with uri_whitespace in
squid.conf configured to "chop" are vulnerable.

All Squid-5.x up to and including 5.0.4 with uri_whitespace in
squid.conf configured to "strip" are vulnerable.

Workaround:

Either,

Configure squid.conf with uri_whitespace deny

Or,

Configure squid.conf with uri_whitespace encode

Contact details for the Squid project:

For installation / upgrade support on binary packaged versions
of Squid: Your first point of contact should be your binary
package vendor.

If you install and build Squid from the original Squid sources
then the squid-users@lists.squid-cache.org mailing list is your
primary support point. For subscription details see
http://www.squid-cache.org/Support/mailing-lists.html.

For reporting of non-security bugs in the latest STABLE release
the squid bugzilla database should be used
http://bugs.squid-cache.org/.

For reporting of security sensitive bugs send an email to the
squid-bugs@lists.squid-cache.org mailing list. It's a closed
list (though anyone can post) and security related bug reports
are treated in confidence until the impact has been established.

Credits:

This vulnerability was discovered by Jianjun Chen from ICSI,
Berkeley.

Fixed by Amos Jeffries of Treehouse Networks Ltd and
Alex Rousskov of The Measurement Factory.

Revision history:

2020-09-01 03:58:36 UTC Initial Report
2020-09-03 03:03:24 UTC CVE Allocation
2020-09-04 04:38:30 UTC Patches released