136 lines
5.3 KiB
Text
136 lines
5.3 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-SA-19:12.telnet Security Advisory
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The FreeBSD Project
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Topic: telnet(1) client multiple vulnerabilities
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Category: contrib
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Module: contrib/telnet
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Announced: 2019-07-24
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Credits: Juniper Networks
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Affects: All supported versions of FreeBSD.
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Corrected: 2019-07-19 15:37:29 UTC (stable/12, 12.0-STABLE)
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2019-07-24 12:51:52 UTC (releng/12.0, 12.0-RELEASE-p8)
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2019-07-19 15:27:53 UTC (stable/11, 11.2-STABLE)
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2019-07-24 12:51:52 UTC (releng/11.2, 11.2-RELEASE-p12)
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2019-07-24 12:51:52 UTC (releng/11.3, 11.3-RELEASE-p1)
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CVE Name: CVE-2019-0053
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For general information regarding FreeBSD Security Advisories,
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including descriptions of the fields above, security branches, and the
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following sections, please visit <URL:https://security.FreeBSD.org/>.
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I. Background
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The telnet(1) command is a TELNET protocol client, used primarily to
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establish terminal sessions across a network.
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II. Problem Description
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Insufficient validation of environment variables in the telnet client
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supplied in FreeBSD can lead to stack-based buffer overflows. A stack-
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based overflow is present in the handling of environment variables when
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connecting via the telnet client to remote telnet servers.
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This issue only affects the telnet client. Inbound telnet sessions to
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telnetd(8) are not affected by this issue.
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III. Impact
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These buffer overflows may be triggered when connecting to a malicious
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server, or by an active attacker in the network path between the client
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and server. Specially crafted TELNET command sequences may cause the
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execution of arbitrary code with the privileges of the user invoking
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telnet(1).
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IV. Workaround
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Do not use telnet(1) to connect to untrusted machines or over an
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untrusted network.
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V. Solution
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Upgrade your vulnerable system to a supported FreeBSD stable or
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release / security branch (releng) dated after the correction date.
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Perform one of the following:
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1) To update your vulnerable system via a binary patch:
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Systems running a RELEASE version of FreeBSD on the i386 or amd64
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platforms can be updated via the freebsd-update(8) utility:
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# freebsd-update fetch
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# freebsd-update install
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2) To update your vulnerable system via a source code patch:
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The following patches have been verified to apply to the applicable
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FreeBSD release branches.
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a) Download the relevant patch from the location below, and verify the
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detached PGP signature using your PGP utility.
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# fetch https://security.FreeBSD.org/patches/SA-19:12/telnet.patch
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# fetch https://security.FreeBSD.org/patches/SA-19:12/telnet.patch.asc
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# gpg --verify telnet.patch.asc
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b) Apply the patch. Execute the following commands as root:
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# cd /usr/src
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# patch < /path/to/patch
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c) Recompile the operating system using buildworld and installworld as
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described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.
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VI. Correction details
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The following list contains the correction revision numbers for each
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affected branch.
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Branch/path Revision
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- -------------------------------------------------------------------------
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stable/12/ r350139
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releng/12.0/ r350281
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stable/11/ r350140
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releng/11.2/ r350281
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releng/11.3/ r350281
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- -------------------------------------------------------------------------
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To see which files were modified by a particular revision, run the
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following command, replacing NNNNNN with the revision number, on a
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machine with Subversion installed:
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# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base
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Or visit the following URL, replacing NNNNNN with the revision number:
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<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>
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VII. References
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<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-0053>
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The latest revision of this advisory is available at
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<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:12.telnet.asc>
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