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Category:   Application (Web Server/CGI)  >   Squid Vendors:
(Red Hat Issues Fix) Squid Processing of Header-Only DNS Messages Lets Remote Users Deny Service
SecurityTracker Alert ID:  1023795
SecurityTracker URL:
CVE Reference:   CVE-2010-0308   (Links to External Site)
Date:  Mar 31 2010
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2.x, 3.0 - 3.0.STABLE21, 3.1 -
Description:   A vulnerability was reported in Squid. A remote user can cause denial of service conditions.

A remote trusted client or external server can send specially crafted DNS packets to cause the target service to become unavailable for a short period of time.

Tomas Hoger of RedHat reported this vulnerability.

Impact:   A remote user can cause denial of service conditions.
Solution:   Red Hat has issued a fix.

The Red Hat advisory is available at:

Vendor URL: (Links to External Site)
Cause:   Input validation error
Underlying OS:  Linux (Red Hat Enterprise)
Underlying OS Comments:  5

Message History:   This archive entry is a follow-up to the message listed below.
Feb 2 2010 Squid Processing of Header-Only DNS Messages Lets Remote Users Deny Service

 Source Message Contents

Subject:  [RHSA-2010:0221-04] Low: squid security and bug fix update

Hash: SHA1

                   Red Hat Security Advisory

Synopsis:          Low: squid security and bug fix update
Advisory ID:       RHSA-2010:0221-04
Product:           Red Hat Enterprise Linux
Advisory URL:
Issue date:        2010-03-30
CVE Names:         CVE-2009-2855 CVE-2010-0308 

1. Summary:

An updated squid package that fixes two security issues and several bugs is
now available for Red Hat Enterprise Linux 5.

The Red Hat Security Response Team has rated this update as having low
security impact. Common Vulnerability Scoring System (CVSS) base scores,
which give detailed severity ratings, are available for each vulnerability
from the CVE links in the References section.

2. Relevant releases/architectures:

RHEL Desktop Workstation (v. 5 client) - i386, x86_64
Red Hat Enterprise Linux (v. 5 server) - i386, ia64, ppc, s390x, x86_64

3. Description:

Squid is a high-performance proxy caching server for web clients,
supporting FTP, Gopher, and HTTP data objects.

A flaw was found in the way Squid processed certain external ACL helper
HTTP header fields that contained a delimiter that was not a comma. A
remote attacker could issue a crafted request to the Squid server, causing
excessive CPU use (up to 100%). (CVE-2009-2855)

Note: The CVE-2009-2855 issue only affected non-default configurations that
use an external ACL helper script.

A flaw was found in the way Squid handled truncated DNS replies. A remote
attacker able to send specially-crafted UDP packets to Squid's DNS client
port could trigger an assertion failure in Squid's child process, causing
that child process to exit. (CVE-2010-0308)

This update also fixes the following bugs:

* Squid's init script returns a non-zero value when trying to stop a
stopped service. This is not LSB compliant and can generate difficulties in
cluster environments. This update makes stopping LSB compliant. (BZ#521926)

* Squid is not currently built to support MAC address filtering in ACLs.
This update includes support for MAC address filtering. (BZ#496170)

* Squid is not currently built to support Kerberos negotiate
authentication. This update enables Kerberos authentication. (BZ#516245)

* Squid does not include the port number as part of URIs it constructs when
configured as an accelerator. This results in a 403 error. This update
corrects this behavior. (BZ#538738)

* the error_map feature does not work if the same handling is set also on
the HTTP server that operates in deflate mode. This update fixes this
issue. (BZ#470843)

All users of squid should upgrade to this updated package, which resolves
these issues. After installing this update, the squid service will be
restarted automatically.

4. Solution:

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at

5. Bugs fixed (

496170 - Add arp filter option
516245 - negotiate support not enabled in squid (for kerberized sso)
518182 - CVE-2009-2855 DoS (100% CPU use) while processing certain external ACL helper HTTP headers
521926 - squid 'stop after stop' is not LSB compliant
538738 - Squid accelerator mode works only if port 80 is opened
556389 - CVE-2010-0308 squid: temporary DoS (assertion failure) triggered by truncated DNS packet (SQUID-2010:1)

6. Package List:

RHEL Desktop Workstation (v. 5 client):




Red Hat Enterprise Linux (v. 5 server):







These packages are GPG signed by Red Hat for security.  Our key and 
details on how to verify the signature are available from

7. References:

8. Contact:

The Red Hat security contact is <>.  More contact
details at

Copyright 2010 Red Hat, Inc.
Version: GnuPG v1.4.4 (GNU/Linux)


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