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UNIRAS Brief - 514/04 - iDEFENSE Security Bulletin - GNU Radius SNMP String Length Integer Overflow Denial of Service Vulnerability.



 
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   UNIRAS (UK Govt CERT) Briefing Notice - 514/04 dated 16.09.04  Time: 15:20  
  UNIRAS is part of NISCC (National Infrastructure Security Co-ordination Centre)
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  UNIRAS material is also available from its website at www.uniras.gov.uk and
         Information about NISCC is available from www.niscc.gov.uk
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Title
=====

iDEFENSE Security Bulletin:

GNU Radius SNMP String Length Integer Overflow Denial of Service Vulnerability.

Detail
====== 

Remote exploitation of an input validation error in version 1.2 of GNU radiusd could allow a 
denial of service.

The vulnerability specifically exists within the asn_decode_string() function defined in 
snmplib/asn1.c. When a very large unsigned number is supplied, it is possible that an integer 
overflow will occur in the bounds-checking code. The daemon will then attempt to reference 
unallocated memory, resulting in an access violation that causes the process to terminate.


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GNU Radius SNMP String Length Integer Overflow Denial of Service Vulnerability

iDEFENSE Security Advisory 09.15.04 www.idefense.com/application/poi/display?id=141&type=vulnerabilities
September 15, 2004

I. BACKGROUND

Radius is used for remote user authentication and accounting.

For more information see:

   http://www.gnu.org/software/radius/radius.html

II. DESCRIPTION

Remote exploitation of an input validation error in version 1.2 of GNU radiusd could allow a 
denial of service.

The vulnerability specifically exists within the asn_decode_string() function defined in 
snmplib/asn1.c. When a very large unsigned number is supplied, it is possible that an integer 
overflow will occur in the bounds-checking code. The daemon will then attempt to reference unallocated 
memory, resulting in an access violation that causes the process to terminate.

III. ANALYSIS

Successful exploitation allows unauthenticated remote attackers to cause the radius daemon (radiusd) 
to crash. This thereby prevents legitimate users from accessing systems reliant upon the affected radius 
server for authentication. This vulnerability does not seem to allow for execution of code; it is a denial 
of service condition only. Exploitation requires that radiusd be compiled with the --enable-snmp option. 
SNMP support is not enabled in the default compile.

IV. DETECTION

iDEFENSE has confirmed that GNU Radius 1.1 and 1.2 are vulnerable, if configured with --enable-snmp at 
compile time.

V. WORKAROUND

Disable SNMP support when building radiusd at compile time. Ingress filtering of UDP port 161 on all 
interfaces that should not be receiving SNMP packets may lessen exposure to this vulnerability in 
affected environments.

VI. VENDOR FIX

The issue has been addressed in maintenance release version number 1.2.94.

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the names CAN-2004-0849 
to these issues. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), 
which standardizes names for security problems.

VIII. DISCLOSURE TIMELINE

09/10/2004   Initial vendor notification
09/10/2004   Initial vendor response
09/15/2004   Public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp

X. LEGAL NOTICES

Copyright (c) 2004 iDEFENSE, Inc.

Permission is granted for the redistribution of this alert electronically. It may not 
be edited in any way without the express written consent of iDEFENSE. If you wish to 
reprint the whole or any part of this alert in any other medium other than electronically, 
please email customerservice@xxxxxxxxxxxx for permission.

Disclaimer: The information in the advisory is believed to be accurate at the time of publishing 
based on currently available information. Use of the information constitutes acceptance for use 
in an AS IS condition. There are no warranties with regard to this information. Neither the author 
nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage 
arising from use of, or reliance on, this information.


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UNIRAS wishes to acknowledge the contributions of iDEFENSE for the information 
contained in this Briefing. 
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This Briefing contains the information released by the original author. Some 
of the information may have changed since it was released. If the vulnerability 
affects you, it may be prudent to retrieve the advisory from the canonical site 
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<End of UNIRAS Briefing>

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