RedHat: 'screen' format string exploit
Posted by LinuxSecurity.com Team   
RedHat Linux Security hole in screen in Red Hat Linux 5.2 and earlier releases
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                   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
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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.Red Hat.com/bugzilla for more info):

N/A

6. RPMs required:

Red Hat Linux 5.2:

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

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

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

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

7. Verification:

MD5 sum                           Package Name
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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.Red Hat.com/corp/contact.html

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

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 

8. References:

N/A


Copyright(c) 2000 Red Hat, Inc.