Originally Published: Thursday, 19 August 1999 Author: Quentin Cregan
Published to: news_enhance_security/Security News Page: 1/1 - [Printable]

RHSA-1999:029-01 DoS in in.telnetd

A denial of service attack has been fixed in in.telnetd.

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--------------------------------------------------------------------- Red Hat, Inc. Security Advisory

Synopsis: Denial of service attack in in.telnetd Advisory ID: RHSA-1999:029-01 Issue date: 1999-08-19 Updated on: Keywords: telnet telnetd Cross references: ---------------------------------------------------------------------

1. Topic:

A denial of service attack has been fixed in in.telnetd.

2. Bug IDs fixed (http://developer.redhat.com/bugzilla/):

4560

3. Relevant releases/architectures:

Red Hat Linux 4.2, 5.2, 6.0, all architectures

4. Obsoleted by:

5. Conflicts with:

6. RPMs required:

Red Hat Linux 4.2:

Intel: ftp://ftp.redhat.com/redhat/updates/4.2/i386/NetKit-B-0.09-11.i386.rpm

Alpha:

ftp://ftp.redhat.com/redhat/updates/4.2/alpha/NetKit-B-0.09-11.alpha.rpm

Sparc:

ftp://ftp.redhat.com/redhat/updates/4.2/sparc/NetKit-B-0.09-11.sparc.rpm

Source packages: ftp://ftp.redhat.com/redhat/updates/4.2/SRPMS/NetKit-B-0.09-11.src.rpm

Red Hat Linux 5.2:

Intel:

ftp://ftp.redhat.com/redhat/updates/5.2/i386/telnet-0.10-28.5.2.i386.rpm

Alpha:

ftp://ftp.redhat.com/redhat/updates/5.2/alpha/telnet-0.10-28.5.2.alpha.rp m

Sparc:

ftp://ftp.redhat.com/redhat/updates/5.2/sparc/telnet-0.10-28.5.2.sparc.rp m

Source packages:

ftp://ftp.redhat.com/redhat/updates/5.2/SRPMS/telnet-0.10-28.5.2.src.rpm

Red Hat Linux 6.0:

Intel: ftp://ftp.redhat.com/redhat/updates/6.0/i386/telnet-0.10-29.i386.rpm

Alpha: ftp://ftp.redhat.com/redhat/updates/6.0/alpha/telnet-0.10-29.alpha.rpm

Sparc: ftp://ftp.redhat.com/redhat/updates/6.0/sparc/telnet-0.10-29.sparc.rpm

Source packages: ftp://ftp.redhat.com/redhat/updates/6.0/SRPMS/telnet-0.10-29.src.rpm

7. Problem description:

in.telnetd attempts to negotiate a compatible terminal type between the local and remote host. By setting the TERM environment variable before connecting, a remote user could cause the system telnetd to open files it should not. Depending on the TERM setting used, this could lead to denial of service attacks.

Thanks go to Michal Zalewski and the Linux Security Audit team for noting this vulnerability.

8. Solution:

For each RPM for your particular architecture, run:

rpm -Uvh

where filename is the name of the RPM.

9. Verification:

MD5 sum Package Name ------------------------------------------------------------------------- - 0c425c34fb77a8309ff10b4143e9b847 i386/NetKit-B-0.09-11.i386.rpm d791d645adeb5fa0147c1058b21cbbac alpha/NetKit-B-0.09-11.alpha.rpm bfbd440845191bbdcf8be21ee59bf6a8 sparc/NetKit-B-0.09-11.sparc.rpm ccd5ab53c423e468d66ca801c90b5ae4 SRPMS/NetKit-B-0.09-11.src.rpm

ef33f3c5ca810d05420e57b5cfcf8928 i386/telnet-0.10-28.5.2.i386.rpm 6dc23437a200193b0bfed23d5f5e6562 alpha/telnet-0.10-28.5.2.alpha.rpm 49c38457cc0a82a680fd9b9634dc8021 sparc/telnet-0.10-28.5.2.sparc.rpm 2f33670a683e3abef0e4914586c71961 SRPMS/telnet-0.10-28.5.2.src.rpm

4360d47490f13d60b8737d28dc88825a i386/telnet-0.10-29.i386.rpm 90213fcdca41a3ed12ab7d92344e7286 alpha/telnet-0.10-29.alpha.rpm 277787dbc39dff8ea84d4b16dcb7a954 sparc/telnet-0.10-29.sparc.rpm 269783a0754d234f7bef0f4717a8dbc2 SRPMS/telnet-0.10-29.src.rpm

These packages are PGP 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

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 --nopgp

10. References:

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