ZDI-07-052: Multiple Kerberos Implementations Authentication Context Stack Overflow Vulnerability http://www.zerodayinitiative.com/advisories/ZDI-07-052.html September 12, 2007
-- CVE ID: CVE-2007-3999
-- Affected Vendor: MIT
-- Affected Products: MIT Kerberos krb5-1.6.2
-- TippingPoint(TM) IPS Customer Protection: TippingPoint IPS customers have been protected against this vulnerability since September 7, 2007 by Digital Vaccine protection filter ID 5503. For further product information on the TippingPoint IPS:
-- Vulnerability Details: This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of MIT Kerberos. Authentication is not required to exploit this vulnerability.
The specific flaw exists in the svcauth_gss_validate() function. By sending a large authentication context over RPC, a stack based buffer overflow occurs, resulting in a situation allowing for remote code execution.
The vulnerable line of the function is: memcpy((caddr_t)buf, oa->oa_base, oa->oa_length);
If 128 < oa->oa_length < 400, the exploitable situation occurs. Over 400 bytes is caught during a separate check for MAX_AUTH_SIZE earlier in the RPC packet decoding process.
-- Vendor Response: MIT has issued an update to correct this vulnerability. More details can be found at:
-- Disclosure Timeline: 2007.07.20 - Vulnerability reported to vendor 2007.09.07 - Digital Vaccine released to TippingPoint customers 2007.09.07 - Coordinated public release of advisory
-- Credit: This vulnerability was discovered by Tenable Network Security.
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