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Red Hat Security Advisory: Format string exploit in screen

Sep 14, 2000, 22:46 (0 Talkback[s])

Date: Thu, 14 Sep 2000 14:20:00 -0400
From: bugzilla@REDHAT.COM
To: BUGTRAQ@SECURITYFOCUS.COM
Subject: [RHSA-2000:058-03] Format string exploit in screen


                   Red Hat, Inc. Security Advisory

Synopsis:          Format string exploit in screen
Advisory ID:       RHSA-2000:058-03
Issue date:        2000-09-07
Updated on:        2000-09-07
Product:           Red Hat Linux
Keywords:          screen exploit format
Cross references:  N/A

1. Topic:

Security hole in screen in Red Hat Linux 5.2 and earlier releases

2. Relevant releases/architectures:

Red Hat Linux 5.2 - i386, i586, i686, alpha, sparc, sparc64, sparcv9

3. Problem description:

Screen allows the user to overload the visual bell with a text message that can be set by the user. This text message is handled as a format string, instead of as a pure string, so maliciously written format strings are allowed to overwrite the stack. Since screen in Red Hat Linux 5.2 and earlier releases was setuid root, this security hole could be exploited to gain a root shell.

4. Solution:

For each RPM for your particular architecture, run:

rpm -Fvh [filename]

where filename is the name of the RPM.

5. Bug IDs fixed (http://bugzilla.redhat.com/bugzilla for more info):

N/A

6. RPMs required:

Red Hat Linux 5.2:

sparc:
ftp://updates.redhat.com/5.2/sparc/screen-3.7.4-4.sparc.rpm

alpha:
ftp://updates.redhat.com/5.2/alpha/screen-3.7.4-4.alpha.rpm

i386:
ftp://updates.redhat.com/5.2/i386/screen-3.7.4-4.i386.rpm

sources:
ftp://updates.redhat.com/5.2/SRPMS/screen-3.7.4-4.src.rpm

7. Verification:

MD5 sum                           Package Name

106a9d1487815b84307182b6ace4eddd 5.2/SRPMS/screen-3.7.4-4.src.rpm
40d13c23ade8c8e9117dd7ff6c9723c9 5.2/alpha/screen-3.7.4-4.alpha.rpm
06bc8d4a829aee9cc21696aaa611771a 5.2/i386/screen-3.7.4-4.i386.rpm
6501aefe36c2f38cc1337c14141b0993 5.2/sparc/screen-3.7.4-4.sparc.rpm
These packages are GPG signed by Red Hat, Inc. for security. Our key is available at:
http://www.redhat.com/corp/contact.html

You can verify each package with the following command:
rpm --checksig <filename>

If you only wish to verify that each package has not been corrupted or tampered with, examine only the md5sum with the following command:
rpm --checksig --nogpg <filename>

8. References:

N/A

Copyright(c) 2000 Red Hat, Inc.