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Category:   Application (Web Server/CGI)  >   Squid Vendors:   [Multiple Authors/Vendors]
(Caldera Issues Fix) Squid Proxy Caching Server Lets Remote Users Conduct Portscans Against Other Hosts Via the Squid Server in Certain Configurations
SecurityTracker Alert ID:  1002156
SecurityTracker URL:
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Aug 7 2001
Impact:   Host/resource access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2.3STABLE3 and 2.3STABLE4 unpatched; including RedHat 7.0 squid, but not RedHat 6.2 or 7.1; Debian is reportedly not vulnerable
Description:   A vulnerability was reported in the Squid proxy caching server that allows remote users to conduct portscans of other hosts via the server when configured as a httpd accelerator (reverse proxy).

Squid reportedly ignores access control lists (ACLs) in httpd_accel mode (only if httpd_accel_host is set and httpd_accel_with_proxy off is set, which is not the default configuration).

The vulnerability can reportedly be triggered with the following steps:

1. Set squid to httpd_accel mode, with a particular host and strict ACLs

2. export httpd_proxy="http://squid-server:port"

3. Use a web browser to scan the target host: lynx http://[targethost]:port/

When a remote user executes the third step, the Squid server will return a http 200 code if the port is open (and some services such as SSH and SMTP will sometimes responsd).

Impact:   A remote user can conduct a portscan against another host via the Squid proxy.
Solution:   The vendor has released a fix for Caldera Linux. See the Source Message for the vendor's advisory containing directions on how to obtain the appropriate fix.
Vendor URL: (Links to External Site)
Cause:   Access control error
Underlying OS:  Linux (Caldera/SCO)

Message History:   This archive entry is a follow-up to the message listed below.
Jul 19 2001 Squid Proxy Caching Server Lets Remote Users Conduct Portscans Against Other Hosts Via the Squid Server in Certain Configurations

 Source Message Contents

Subject:  Security Update [CSSA-2001-029.0] Linux - Squid configuration problems

Hash: SHA1

		   Caldera International, Inc.  Security Advisory

Subject:		Linux - Squid configuration problems
Advisory number: 	CSSA-2001-029.0
Issue date: 		2001, August 06
Cross reference:

1. Problem Description

   There is a security problem with Squid, a proxy server shipped as part
   of OpenLinux 3.1 Server. If Squid is configured for accelerator mode
   (setting http_accel_with_proxy off), any request to Squid is allowed.
   Malicious users may use your proxy to portscan remote systems, forge
   email, and other activities.

2. Vulnerable Versions

   System                       Package
   OpenLinux 2.3                 not vulnerable                
   OpenLinux eServer 2.3.1       not vulnerable                
   and OpenLinux eBuilder                                      
   OpenLinux eDesktop 2.4        not vulnerable                
   OpenLinux Server 3.1          All packages previous to      
   OpenLinux Workstation 3.1     not vulnerable                

3. Solution



   The proper solution is to upgrade to the latest packages.

4. OpenLinux 2.3

    not vulnerable

5. OpenLinux eServer 2.3.1 and OpenLinux eBuilder for ECential 3.0

    not vulnerable

6. OpenLinux eDesktop 2.4

    not vulnerable

7. OpenLinux 3.1 Server

    7.1 Location of Fixed Packages

       The upgrade packages can be found on Caldera's FTP site at:

       The corresponding source code package can be found at:

   7.2 Verification

       1779083edd38872f2ac15c219131d1ba  RPMS/squid-2.4.STABLE1-7.i386.rpm
       e5020ebf7aef60878139cdac81737212  SRPMS/squid-2.4.STABLE1-7.src.rpm

   7.3 Installing Fixed Packages

       Upgrade the affected packages with the following commands:

         rpm -Fvh squid-2.4.STABLE1-7.i386.rpm

8. OpenLinux 3.1 Workstation

    not vulnerable

9. References

   This and other Caldera security resources are located at:

   This security fix closes Caldera's internal Problem Report 10294.

10. Disclaimer

   Caldera International, Inc. is not responsible for the misuse of
   any of the information we provide on this website and/or through our
   security advisories. Our advisories are a service to our customers
   intended to promote secure installation and use of Caldera OpenLinux.
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see


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