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Multiple implementations of the RADIUS protocol do not adequately validate the vendor-length of the vendor-specific attributes

Vulnerability Note VU#936683

Original Release Date: 2002-03-04 | Last Revised: 2002-04-16

Overview

Various RADIUS servers and clients permit the passing of vendor-specific and user-specific attributes. Several implementations of RADIUS fail to check the Vendor-Length of the Vendor-Specific attribute. It's possible to cause a denial of service against RADIUS servers with a malformed Vendor-Specific attribute.

Description

RADIUS servers and clients fail to validate the Vendor-Length inside Vendor-Specific attributes. The Vendor-Length shouldn't be less than 2. If Vendor-Length is less than 2, the RADIUS server (or client) calculates the attribute length as a negative number. The attribute length is then used in various functions. In most RADIUS servers the function that performs this calculation is rad_recv() or radrecv(). Some applications may use the same logic to validate user-specific attributes and be vulnerable via the same method. For example, YARDRadius contains this vulnerability in the handling of the User-Specific attributes only.

Impact

It is possible to cause a denial of service against the RADIUS server with a malformed Vendor-Specific attribute. Though unlikely, if a RADIUS client processes the Vendor-Specific attribute contained in a server response, then the client may also be vulnerable.

Solution

Apply a patch or upgrade to the version specified by your vendor.

Vendor Information

936683
 

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References

Acknowledgements

Our thanks to 3APA3A <3APA3A@SECURITY.NNOV.RU> for the report and analysis of this vulnerability.

This document was written by Jason Rafail and is based on information provided by 3APA3A.

Other Information

CVE IDs: CVE-2001-1377
CERT Advisory: CA-2002-06
Severity Metric: 1.77
Date Public: 2001-11-29
Date First Published: 2002-03-04
Date Last Updated: 2002-04-16 18:58 UTC
Document Revision: 18

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