FreeBSD Security Advisories
2009-Feb-16 14:02 UTC
FreeBSD Security Advisory FreeBSD-SA-09:05.telnetd
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============================================================================FreeBSD-SA-09:05.telnetd
Security Advisory
The FreeBSD Project
Topic: telnetd code execution vulnerability
Category: core
Module: contrib
Announced: 2009-02-16
Affects: FreeBSD 7.x
Corrected: 2009-02-16 21:56:17 UTC (RELENG_7, 7.1-STABLE)
2009-02-16 21:56:17 UTC (RELENG_7_1, 7.1-RELEASE-p10)
2009-02-16 21:56:17 UTC (RELENG_7_0, 7.0-RELEASE-p3)
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:http://security.FreeBSD.org/>.
I. Background
The FreeBSD telnet daemon, telnetd(8), implements the server side of the
TELNET virtual terminal protocol. It has been disabled by default in
FreeBSD since August 2001, and due to the lack of cryptographic security
in the TELNET protocol, it is strongly recommended that the SSH protocol
be used instead. The FreeBSD telnet daemon can be enabled via the
/etc/inetd.conf configuration file and the inetd(8) daemon.
The TELNET protocol allows a connecting client to specify environment
variables which should be set in any created login session; this is used,
for example, to specify terminal settings.
II. Problem Description
In order to prevent environment variable based attacks, telnetd(8)
"scrubs"
its environment; however, recent changes in FreeBSD's environment-handling
code rendered telnetd's scrubbing inoperative, thereby allowing potentially
harmful environment variables to be set.
III. Impact
An attacker who can place a specially-constructed file onto a target system
(either by legitimately logging into the system or by exploiting some other
service on the system) can execute arbitrary code with the privileges of
the user running the telnet daemon (usually root).
IV. Workaround
No workaround is available, but systems which are not running the telnet
daemon are not vulnerable.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 7-STABLE, or to the RELENG_7_1 or
RELENG_7_0 security branch dated after the correction date.
2) To patch your present system:
The following patches have been verified to apply to FreeBSD 7.0 and 7.1
systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
# fetch http://security.FreeBSD.org/patches/SA-09:05/telnetd.patch
# fetch http://security.FreeBSD.org/patches/SA-09:05/telnetd.patch.asc
b) Execute the following commands as root:
# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libtelnet
# make obj && make depend && make
# cd /usr/src/libexec/telnetd
# make obj && make depend && make && make install
VI. Correction details
The following list contains the revision numbers of each file that was
corrected in FreeBSD.
CVS:
Branch Revision
Path
- -------------------------------------------------------------------------
RELENG_7
src/contrib/telnet/telnetd/sys_term.c 1.18.22.1
RELENG_7_1
src/UPDATING 1.507.2.13.2.6
src/sys/conf/newvers.sh 1.72.2.9.2.7
src/contrib/telnet/telnetd/sys_term.c 1.18.30.2
RELENG_7_0
src/UPDATING 1.507.2.3.2.14
src/sys/conf/newvers.sh 1.72.2.5.2.14
src/contrib/telnet/telnetd/sys_term.c 1.18.26.1
- -------------------------------------------------------------------------
Subversion:
Branch/path Revision
- -------------------------------------------------------------------------
stable/7/ r188699
releng/7.1/ r188699
releng/7.0/ r188699
- -------------------------------------------------------------------------
VII. References
http://lists.grok.org.uk/pipermail/full-disclosure/2009-February/067954.html
The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-09:05.telnetd.asc
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FreeBSD Security Advisories
2009-Feb-16 14:02 UTC
FreeBSD Security Advisory FreeBSD-SA-09:05.telnetd
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Hash: SHA1
============================================================================FreeBSD-SA-09:05.telnetd
Security Advisory
The FreeBSD Project
Topic: telnetd code execution vulnerability
Category: core
Module: contrib
Announced: 2009-02-16
Affects: FreeBSD 7.x
Corrected: 2009-02-16 21:56:17 UTC (RELENG_7, 7.1-STABLE)
2009-02-16 21:56:17 UTC (RELENG_7_1, 7.1-RELEASE-p10)
2009-02-16 21:56:17 UTC (RELENG_7_0, 7.0-RELEASE-p3)
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:http://security.FreeBSD.org/>.
I. Background
The FreeBSD telnet daemon, telnetd(8), implements the server side of the
TELNET virtual terminal protocol. It has been disabled by default in
FreeBSD since August 2001, and due to the lack of cryptographic security
in the TELNET protocol, it is strongly recommended that the SSH protocol
be used instead. The FreeBSD telnet daemon can be enabled via the
/etc/inetd.conf configuration file and the inetd(8) daemon.
The TELNET protocol allows a connecting client to specify environment
variables which should be set in any created login session; this is used,
for example, to specify terminal settings.
II. Problem Description
In order to prevent environment variable based attacks, telnetd(8)
"scrubs"
its environment; however, recent changes in FreeBSD's environment-handling
code rendered telnetd's scrubbing inoperative, thereby allowing potentially
harmful environment variables to be set.
III. Impact
An attacker who can place a specially-constructed file onto a target system
(either by legitimately logging into the system or by exploiting some other
service on the system) can execute arbitrary code with the privileges of
the user running the telnet daemon (usually root).
IV. Workaround
No workaround is available, but systems which are not running the telnet
daemon are not vulnerable.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 7-STABLE, or to the RELENG_7_1 or
RELENG_7_0 security branch dated after the correction date.
2) To patch your present system:
The following patches have been verified to apply to FreeBSD 7.0 and 7.1
systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
# fetch http://security.FreeBSD.org/patches/SA-09:05/telnetd.patch
# fetch http://security.FreeBSD.org/patches/SA-09:05/telnetd.patch.asc
b) Execute the following commands as root:
# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/libtelnet
# make obj && make depend && make
# cd /usr/src/libexec/telnetd
# make obj && make depend && make && make install
VI. Correction details
The following list contains the revision numbers of each file that was
corrected in FreeBSD.
CVS:
Branch Revision
Path
- -------------------------------------------------------------------------
RELENG_7
src/contrib/telnet/telnetd/sys_term.c 1.18.22.1
RELENG_7_1
src/UPDATING 1.507.2.13.2.6
src/sys/conf/newvers.sh 1.72.2.9.2.7
src/contrib/telnet/telnetd/sys_term.c 1.18.30.2
RELENG_7_0
src/UPDATING 1.507.2.3.2.14
src/sys/conf/newvers.sh 1.72.2.5.2.14
src/contrib/telnet/telnetd/sys_term.c 1.18.26.1
- -------------------------------------------------------------------------
Subversion:
Branch/path Revision
- -------------------------------------------------------------------------
stable/7/ r188699
releng/7.1/ r188699
releng/7.0/ r188699
- -------------------------------------------------------------------------
VII. References
http://lists.grok.org.uk/pipermail/full-disclosure/2009-February/067954.html
The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-09:05.telnetd.asc
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Hi, It seems that you got the patch levels wrong in this announcement, should it not be: 2009-02-16 21:56:17 UTC (RELENG_7, 7.1-STABLE) 2009-02-16 21:56:17 UTC (RELENG_7_1, 7.1-RELEASE-p3) 2009-02-16 21:56:17 UTC (RELENG_7_0, 7.0-RELEASE-p10) Rather than: 2009-02-16 21:56:17 UTC (RELENG_7, 7.1-STABLE) 2009-02-16 21:56:17 UTC (RELENG_7_1, 7.1-RELEASE-p10) 2009-02-16 21:56:17 UTC (RELENG_7_0, 7.0-RELEASE-p3) Regards Tom Judge FreeBSD Security Advisories wrote:> -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > ============================================================================> FreeBSD-SA-09:05.telnetd Security Advisory > The FreeBSD Project > > Topic: telnetd code execution vulnerability > > Category: core > Module: contrib > Announced: 2009-02-16 > Affects: FreeBSD 7.x > Corrected: 2009-02-16 21:56:17 UTC (RELENG_7, 7.1-STABLE) > 2009-02-16 21:56:17 UTC (RELENG_7_1, 7.1-RELEASE-p10) > 2009-02-16 21:56:17 UTC (RELENG_7_0, 7.0-RELEASE-p3) > > For general information regarding FreeBSD Security Advisories, > including descriptions of the fields above, security branches, and the > following sections, please visit <URL:http://security.FreeBSD.org/>. > > I. Background > > The FreeBSD telnet daemon, telnetd(8), implements the server side of the > TELNET virtual terminal protocol. It has been disabled by default in > FreeBSD since August 2001, and due to the lack of cryptographic security > in the TELNET protocol, it is strongly recommended that the SSH protocol > be used instead. The FreeBSD telnet daemon can be enabled via the > /etc/inetd.conf configuration file and the inetd(8) daemon. > > The TELNET protocol allows a connecting client to specify environment > variables which should be set in any created login session; this is used, > for example, to specify terminal settings. > > II. Problem Description > > In order to prevent environment variable based attacks, telnetd(8) "scrubs" > its environment; however, recent changes in FreeBSD's environment-handling > code rendered telnetd's scrubbing inoperative, thereby allowing potentially > harmful environment variables to be set. > > III. Impact > > An attacker who can place a specially-constructed file onto a target system > (either by legitimately logging into the system or by exploiting some other > service on the system) can execute arbitrary code with the privileges of > the user running the telnet daemon (usually root). > > IV. Workaround > > No workaround is available, but systems which are not running the telnet > daemon are not vulnerable. > > V. Solution > > Perform one of the following: > > 1) Upgrade your vulnerable system to 7-STABLE, or to the RELENG_7_1 or > RELENG_7_0 security branch dated after the correction date. > > 2) To patch your present system: > > The following patches have been verified to apply to FreeBSD 7.0 and 7.1 > systems. > > a) Download the relevant patch from the location below, and verify the > detached PGP signature using your PGP utility. > > # fetch http://security.FreeBSD.org/patches/SA-09:05/telnetd.patch > # fetch http://security.FreeBSD.org/patches/SA-09:05/telnetd.patch.asc > > b) Execute the following commands as root: > > # cd /usr/src > # patch < /path/to/patch > # cd /usr/src/lib/libtelnet > # make obj && make depend && make > # cd /usr/src/libexec/telnetd > # make obj && make depend && make && make install > > VI. Correction details > > The following list contains the revision numbers of each file that was > corrected in FreeBSD. > > CVS: > > Branch Revision > Path > - ------------------------------------------------------------------------- > RELENG_7 > src/contrib/telnet/telnetd/sys_term.c 1.18.22.1 > RELENG_7_1 > src/UPDATING 1.507.2.13.2.6 > src/sys/conf/newvers.sh 1.72.2.9.2.7 > src/contrib/telnet/telnetd/sys_term.c 1.18.30.2 > RELENG_7_0 > src/UPDATING 1.507.2.3.2.14 > src/sys/conf/newvers.sh 1.72.2.5.2.14 > src/contrib/telnet/telnetd/sys_term.c 1.18.26.1 > - ------------------------------------------------------------------------- > > Subversion: > > Branch/path Revision > - ------------------------------------------------------------------------- > stable/7/ r188699 > releng/7.1/ r188699 > releng/7.0/ r188699 > - ------------------------------------------------------------------------- > > VII. References > > http://lists.grok.org.uk/pipermail/full-disclosure/2009-February/067954.html > > The latest revision of this advisory is available at > http://security.FreeBSD.org/advisories/FreeBSD-SA-09:05.telnetd.asc > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.9 (FreeBSD) > > iEYEARECAAYFAkmZ4dwACgkQFdaIBMps37JI2gCfZsCqw/ev/qVKELwNiFxj8zra > aooAn0GU4wBW7jBulFhrSyXtKVlgs18B > =joA6 > -----END PGP SIGNATURE----- > _______________________________________________ > freebsd-security-notifications@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-security-notifications > To unsubscribe, send any mail to "freebsd-security-notifications-unsubscribe@freebsd.org" >