AUSCERT External Security Bulletin Redistribution

               ESB-97.095 -- Sun Security Bulletin #00147
		         Vulnerability in talkd
                              25 July 1997


Sun Microsystems, Inc. has released the following advisory concerning a
vulnerability in the talkd program.  This vulnerability may allow local
and remote users to gain root access.  This vulnerability has been publically
discussed and reported in AUSCERT advisory AA-97.01.

The following security bulletin is provided as a service to AUSCERT's
members.  As AUSCERT did not write this document, AUSCERT has had no
control over its content.  As such, the decision to use any or all of this
information is the responsibility of each user or organisation, and should
be done so in accordance with site policies and procedures.

Contact information for Sun Microsystems, Inc. is included in the Security
Bulletin below.  If you have any questions or need further information,
please contact them directly.

A mirror of the patches mentioned in this advisory are available from:


Previous advisories and external security bulletins can be retrieved from:


If you believe that your system has been compromised, contact AUSCERT or your
representative in FIRST (Forum of Incident Response and Security Teams).

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 4477
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
	AUSCERT personnel answer during Queensland business hours
	which are GMT+10:00 (AEST).
	On call after hours for emergencies.

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 		   Sun Microsystems, Inc. Security Bulletin
Bulletin Number:	#00147
Date: 			July 24, 1997
Cross-Ref:		AUSCERT AA-97.01, CERT CA-97.04
Title:			Vulnerability in talkd

Permission is granted for the redistribution of this Bulletin, so long as 
the Bulletin is not edited and is attributed to Sun Microsystems. Portions 
may also be excerpted for re-use in other security advisories so long as 
proper attribution is included.

Any other use of this information without the express written consent of 
Sun Microsystems is prohibited. Sun Microsystems expressly disclaims all 
liability for any misuse of this information by any third party.

1.  Bulletins Topics

    Sun announces the release of patches for Solaris 2.5.1, 2.5, 2.4, and 2.3 
    (SunOS 5.5.1, 5.5, 5.4, and 5.3), SunOS 4.1.4 and 4.1.3_U1 which relate to 
    a vulnerability in the talkd program.

    Sun strongly recommends that you install the patches listed in section 4 
    immediately on systems running SunOS 5.5.1, 5.5, 5.4, 5.3, 4.1.4, and 
    4.1.3_U1. Exploit information is publicly available.

2.  Who is Affected
    Vulnerable:  SunOS versions 5.5.1, 5.5.1_x86, 5.5, 5.5_x86,
                                5.4, 5.4_x86, 5.3, 4.1.4, and 4.1.3_U1
    The vulnerability is fixed in the upcoming release of Solaris.

3.  Understanding the Vulnerability

    The program talk provides a two-way, screen-oriented conversation between
    users. The daemon talkd notitifes a user that another user wishes to 
    initiate a talk conversation. When a user initiates a talk conversation, 
    talkd performs a name service lookup for the name of the initiating host. 
    Due to insufficient bounds checking on the buffer where the hostname is 
    stored, it is possible to overwrite the internal stack space of the talkd 
    program. As talkd is setuid root, this vulnerability may be exploited by 
    intruders to remotely execute arbitrary commands with root privileges. To 
    exploit this vulnerability, attackers have to be able to make a network 
    connection to the vulnerable talkd program and provide corrupt hostname 
    information to that host.

4.  List of Patches

    The vulnerability in talkd is fixed by the following patches:

    OS version		Patch ID
    __________		________
    SunOS 5.5.1		104692-01	
    SunOS 5.5.1_x86	104693-01	
    SunOS 5.5		104690-01	
    SunOS 5.5_x86	104691-01	
    SunOS 5.4		104701-01	
    SunOS 5.4_x86	104702-01	
    SunOS 5.3		104698-01
    SunOS 4.1.4		104998-01
    SunOS 4.1.3_U1	104997-01			

5.  Checksum Table

    The checksum table below shows the BSD checksums (SunOS 4.1.x: /bin/sum; 
    SunOS 5.x: /usr/ucb/sum), SVR4 checksums (SunOS 5.x: /usr/bin/sum), and 
    the MD5 digital signatures for the above-mentioned patches that are 
    available from:
    These checksums may not apply if you obtain patches from your answer

File Name	  BSD	     SVR4	  MD5
_______________   ________   _________    ________________________________
104692-01.tar.Z   05337 97   5296 194     0F45E5B9CCAD276AE166CAFFE9110799
104693-01.tar.Z   44228 97   39970 194    32D62F61E350AA6B50FBD2A4BA1059CA
104690-01.tar.Z   26808 97   47810 194    E4360074D6BB751C22406F1962556138
104691-01.tar.Z   07788 97   37926 194    B3519CA85BCD2CD818B1712B655E260F
104701-01.tar.Z   03035 85   2323 169     FCBEEAADE24029B9E5B0FB3CFAEE9CCE
104702-01.tar.Z   14433 85   29616 169    922599D5FF853181A9671070C7213F0D
104698-01.tar.Z   25487 85   52869 169    337DD394B381E4D61BA7E590ED1BBAD7
104998-01.tar.Z   46836 10   15721 19     8C62C5B5E0965BB0E0D3B5B835D98670
104997-01.tar.Z   21171 10   10506 19     DE1AE78A37570FD597AA39844554A3C7
Sun acknowledges with thanks AUSCERT and CERT/CC for their assistance in the 
preparation of this bulletin.

Sun, AUSCERT, and CERT/CC are members of FIRST, the Forum of Incident Response 
and Security Teams. For more information about FIRST, visit the FIRST web site 
at "http://www.first.org/".

A.  Patches listed in this bulletin are available to all Sun customers via 
    World Wide Web at:
    Customers with Sun support contracts can also obtain patches from local 
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