TippingPoint Zero Day Initiative

Multiple Kerberos Implementations Authentication Context Stack Overflow Vulnerability

ZDI-07-052: September 12th, 2007

CVE ID

Affected Vendors

    MIT

Affected Products

    Kerberos

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
    2007-09-12 - Coordinated public release of advisory

Credit

This vulnerability was discovered by:
    Tenable Network Security