Red Hat Security Advisory: Format string exploit in screen

Date: Thu, 14 Sep 2000 14:20:00 -0400
From: [email protected]
To: [email protected]
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

2. Relevant releases/architectures:

Red Hat Linux 5.2 – i386, i586, i686, alpha, sparc, sparc64,

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):


6. RPMs required:

Red Hat Linux 5.2:





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:

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:


Copyright(c) 2000 Red Hat, Inc.