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CERT Coordination Center


Kerberos client code buffer overflow in kdc_reply_cipher()

Vulnerability Note VU#759265

Original Release Date: 2000-12-19 | Last Revised: 2001-01-11

Overview

There is a buffer overflow is the kdc_reply_cipher() function of KTH Kerberos. This buffer overflow may be exploitable to allow an attacker to gain root privileges, and can be used to deny service.

Description

The buffer overflow occurs in the parsing of an authentication reply in the kdc_reply_cipher() function of kdc_reply.c. The attacker may supply a packet length greater than that which was actually sent, causing a memcpy() call to overwrite the stack with data in memory adjacent to the packet buffer. It is not clear if the attacker has control of the memory adjacent to this packet buffer, so it is not clear that the vulnerability is exploitable to gain privileges. The vulnerability could however be exploited causing the server to crash. To exploit this vulnerability, the attacker must trick the client into making a request to a malicious KDC. The attacker could accomplish this redirection by defining the krb4_proxy or KRBCONFDIR environment variables as described in VU#602625, or by manipulating DNS information.

Impact

An attacker can cause a service to crash if they can redirect authentication requests to a malicious KDC under their control. While it is not clear if this vulnerability is exploitable to gain privileges, an attacker may be able to execute arbitrary code on a client making an authentication request to the malicious server. Since the client typically executes as root, root privileges may be gained.

Solution

Apply a patch from your vendor.

Vendor Information

759265
Expand all

FreeBSD

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Vulnerable

Vendor Statement

FreeBSD includes the externally maintained KTH Kerberos software as an optional component of the FreeBSD base system. Therefore, systems which have installed the Kerberos 4 components are vulnerable to these problems as described in the CERT advisory. Patches have been committed to the FreeBSD source tree and an advisory will be released shortly detailing the precise impact on vulnerable FreeBSD systems.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Apple

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Not Vulnerable

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Compaq Computer Corporation

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Not Vulnerable

Vendor Statement

Not vulnerable.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Fujitsu

Notified:  December 11, 2000 Updated:  January 11, 2001

Status

  Not Vulnerable

Vendor Statement

Fujitsu's UXP/V operating system is not vulnerable to the bugs in VU#602625, VU#759265, and VU#426273, because UXP/V does not support Kerberos.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

IBM

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Not Vulnerable

Vendor Statement

Our AIX operating system does not include KTH Kerberos IV, so it is not vulnerable to the security exploits described here.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Microsoft

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Not Vulnerable

Vendor Statement

Windows 2000 does not support Kerb IV. W2K has completely different implementation of the protocol and is not vulnerable to the specific buffer overflow condition using memcpy identified by VU#759265. (Note that buffer overrun as a general implementation problem is one we are continuously on guard against through our buffer overrun examination tools, internal code reviews, and in the case of kerberos implementation, an external security code review).

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

BSDI

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Caldera

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Data General

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Debian

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Hewlett Packard

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

KTH Kerberos

Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

NetBSD

Notified:  December 11, 2000 Updated:  January 11, 2001

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

NetBSD has produced an advisory on this issue. It is available from:

ftp://ftp.NetBSD.ORG/pub/NetBSD/misc/security/advisories/NetBSD-SA2000-017.txt.asc

They appear to be vulnerable to this issue.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

OpenBSD

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

RedHat

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

SGI

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Sony

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Sun

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.

Washington University

Notified:  December 11, 2000 Updated:  December 14, 2000

Status

  Unknown

Vendor Statement

WU-FTPD 2.6.1 supports Kerberos in one of two ways:

    • Via PAM: in which case we defer any statement of vulnerability to the PAM maintainers.
    • Via direct calls: in which case we are probably as vulnerable as any other service using Kerberos for user authentication.

For WU-FTPD systems using Kerberos, especially those which do not use shared libraries, I would recommend re-compiling (specifically, re-linking) the daemon to ensure an updated Kerberos runtime is used.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.


CVSS Metrics

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A

References

Credit

Thanks to Jouko Pynnönen for reporting this vulnerability to the CERT/CC, and to Assar Westerlund for assisting in the development of this document.

This document was written by Cory F Cohen.

Other Information

CVE IDs: None
Severity Metric: 3.49
Date Public: 2000-12-09
Date First Published: 2000-12-19
Date Last Updated: 2001-01-11 15:57 UTC
Document Revision: 8

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