Public Vulnerability Reports

UnixWare PPPTalk Local Root Vulnerability

10.15.02

BACKGROUND

PPPTalk is an administrative interface for the PPP subsystem. It controls the operation of the PPP daemon.

DESCRIPTION

Attackers can gain super user privileges by exploiting a vulnerability in PPPTalk on systems running PPPD. The crux of the problem lies in that the effective user id is not reset before ppptalk starts the shell. By taking advantage of a shell escape feature in the ppptalk application an attacker can gain root privileges. The following is a snapshot of the exploit in action:

$ ppptalk
ppp >!./ppptalk_exploit
# id
uid=0(root) gid=1(other) groups=0(root), 1(other), 2(bin), 3(sys), 4(adm), 5(uucp),
6(mail), 7(tty), 8(audit), 10(nuucp), 12(daemon), 23(cron), 25(dtadmin), 47(priv), 9(lp)

ANALYSIS

Any local user can launch this attack and obtain super user privileges. Successful exploitation is trivial and provides the attacker with full control over the target system.

iDEFENSE has proof of concept exploit code demonstrating the impact of this vulnerability.

DETECTION

Exploitation is possible if ppptalk is installed set user id root and pppd is running, both of these conditions are met on a default installation of The SCO Group's UnixWare.

WORKAROUND

Remove the setuid bit from the ppptalk binary by executing the following command:

# chmod -s `which ppptalk` 

VENDOR RESPONSE

The vendor has provided the following fixes:

Caldera UnixWare 7.1.1:

    Caldera Patch erg711697a.Z
    ftp://ftp.caldera.com/pub/updates/UnixWare/CSSA-2001-SCO.27/erg711697a.Z


Caldera OpenUnix 8.0:

    Caldera Patch erg712071.pkg.Z
    ftp://ftp.caldera.com/pub/updates/OpenUNIX/CSSA-2002-SCO.27/erg712071.pkg.Z

CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has assigned CAN-2002-0827 to this issue.

DISCLOSURE TIMELINE

10/02/2002   Exploit acquired by iDEFENSE
10/05/2002     Initial vendor notification
10/08/2002   iDEFENSE Clients notified
10/15/2002   Public Disclosure

CREDIT

Texonet Co. is credited with this discovery.

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LEGAL NOTICES

Copyright © 2004 Verisign, Inc.

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