ZDI-07-052: Multiple Kerberos Implementations Authentication Context Stack Overflow Vulnerability

Type securityvulns
Reporter Securityvulns
Modified 2007-09-13T00:00:00


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.

-- About the Zero Day Initiative (ZDI): Established by TippingPoint, a division of 3Com, The Zero Day Initiative (ZDI) represents a best-of-breed model for rewarding security researchers for responsibly disclosing discovered vulnerabilities.

Researchers interested in getting paid for their security research through the ZDI can find more information and sign-up at:


The ZDI is unique in how the acquired vulnerability information is used. 3Com does not re-sell the vulnerability details or any exploit code. Instead, upon notifying the affected product vendor, 3Com provides its customers with zero day protection through its intrusion prevention technology. Explicit details regarding the specifics of the vulnerability are not exposed to any parties until an official vendor patch is publicly available. Furthermore, with the altruistic aim of helping to secure a broader user base, 3Com provides this vulnerability information confidentially to security vendors (including competitors) who have a vulnerability protection or mitigation product.