Squid Proxy Cache Security Update Advisory SQUID-2020:1

Advisory ID:        SQUID-2020:1
Date:               February 03, 2020
Summary:            Improper Input Validation issues
                    in HTTP Request processing.
Affected versions:  Squid 2.x -> 2.7.STABLE9
                    Squid 3.x -> 3.5.28
                    Squid 4.x -> 4.9
Fixed in version:   Squid 4.10


Problem Description:

 Due to incorrect input validation Squid can interpret crafted
 HTTP requests in unexpected ways to access server resources
 prohibited by earlier security filters.

 Due to incorrect buffer management a remote client can cause
 a buffer overflow in a Squid acting as reverse-proxy.



 This issue allows attackers to perform denial of service on the
 proxy and all clients using it.

 This issue potentially allows attackers to bypass security access
 controls in systems between client and proxy.

 This issue potentially allows remote code execution under the
 proxy low-privilege level. While restricted, it does have access
 to a wide range of information about the network structure and
 other clients using the proxy.

 This issue is limited to Squid acting as a reverse-proxy. Some
 effects also require allow_direct permissions.


Updated Packages:

 This bug is fixed by Squid version 4.10.

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

Squid 3.5:

Squid 4.8 and older:

Squid 4.9:

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


Determining if your version is vulnerable:

 All Squid-2.x up to and including 2.7.STABLE9 with http_port
 'accel' or 'vhost' options configured are vulnerable.

 All Squid-3.x up to and including 3.5.28 with http_port
 'accel' or 'vhost' options configured are vulnerable.

 All Squid-4.x up to and including 4.9 with with http_port
 'accel' option configured are vulnerable.

To determine what port options are configured use the command:

 squid -k parse | grep -E _port



 There are no workarounds.


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 your install and build Squid from the original Squid sources
 then the squid-us...@lists.squid-cache.org mailing list is your
 primary support point. For subscription details see

 For reporting of non-security bugs in the latest STABLE release
 the squid bugzilla database should be used

 For reporting of security sensitive bugs send an email to the
 squid-b...@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.



 Security Bypass and Server Side Request Forgery vulnerability
 was discovered by Regis Leroy (regilero from Makina Corpus).

 Denial of Service and Remote Code Execution vulnerability was
 discovered by Guido Vranken.

 Fixed by Amos Jeffries of Treehouse Networks Ltd. and Guido


Revision history:

 2019-07-24 11:52:51 UTC Initial Report
 2019-08-13 13:50:06 UTC Initial Patches Released
 2019-10-05 02:05:23 UTC Additional Report
 2019-12-12 03:27:40 UTC Additional Patches Released
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