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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2019.2792 telnet(1) client multiple vulnerabilities 26 July 2019 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: telnet Publisher: FreeBSD Operating System: FreeBSD Impact/Access: Execute Arbitrary Code/Commands -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2019-0053 Reference: ESB-2019.2563 Original Bulletin: https://security.freebsd.org/advisories/FreeBSD-SA-19:12.telnet.asc - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-19:12.telnet Security Advisory The FreeBSD Project Topic: telnet(1) client multiple vulnerabilities Category: contrib Module: contrib/telnet Announced: 2019-07-24 Credits: Juniper Networks Affects: All supported versions of FreeBSD. Corrected: 2019-07-19 15:37:29 UTC (stable/12, 12.0-STABLE) 2019-07-24 12:51:52 UTC (releng/12.0, 12.0-RELEASE-p8) 2019-07-19 15:27:53 UTC (stable/11, 11.2-STABLE) 2019-07-24 12:51:52 UTC (releng/11.2, 11.2-RELEASE-p12) 2019-07-24 12:51:52 UTC (releng/11.3, 11.3-RELEASE-p1) CVE Name: CVE-2019-0053 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>. I. Background The telnet(1) command is a TELNET protocol client, used primarily to establish terminal sessions across a network. II. Problem Description Insufficient validation of environment variables in the telnet client supplied in FreeBSD can lead to stack-based buffer overflows. A stack- based overflow is present in the handling of environment variables when connecting via the telnet client to remote telnet servers. This issue only affects the telnet client. Inbound telnet sessions to telnetd(8) are not affected by this issue. III. Impact These buffer overflows may be triggered when connecting to a malicious server, or by an active attacker in the network path between the client and server. Specially crafted TELNET command sequences may cause the execution of arbitrary code with the privileges of the user invoking telnet(1). IV. Workaround Do not use telnet(1) to connect to untrusted machines or over an untrusted network. V. Solution Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. Perform one of the following: 1) To update your vulnerable system via a binary patch: Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install 2) To update your vulnerable system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch https://security.FreeBSD.org/patches/SA-19:12/telnet.patch # fetch https://security.FreeBSD.org/patches/SA-19:12/telnet.patch.asc # gpg --verify telnet.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile the operating system using buildworld and installworld as described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - - ------------------------------------------------------------------------- stable/12/ r350139 releng/12.0/ r350281 stable/11/ r350140 releng/11.2/ r350281 releng/11.3/ r350281 - - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing NNNNNN with the revision number: <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN> VII. References <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-0053> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:12.telnet.asc> - -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAl04WltfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cLOzA//YxRZNUr+d8B+t6DnBUbVvthJiY9sQ1YPXUIJmp4QA7wvXr5UjURw+6qv raxEp6JmF06wZK4RjeIFckQD6s2wnjO5VHO80Zbs0nD4NejQGeDAIlVdKqofOtJv bBQNSY3vPAtumyfElc+N19rKetAjGbsUjOMbn87GlWrit4lqcavBQsdmSlQB5gVA dFAFsVxr+ujjATnrCmIpFiaDk0unyJ7Gtz7jiM9I8xZueJtM49/9kNCFFLKCMUl8 HpB2k0cb18GVNJoKtzo1nELOM/oIJVO5HZt1fmYG/RgeL1BSyzg4q/5jXJQopJ2h Qax7fmMP+RpGGrfp9Uom63tj79eQk2NirpUtfAaYkfGKzj6fNcq/7jxZfbobx0R8 uTiF88mlv2/SGxpo11Z/QBqOSYTQtjDRYJvjCo77g7YW8HauECC3tiklpPfFOIO8 m5qNOORKI74Do377GBF3gxDF2T8ILwj1j7nKHf3apotvQXJkkbpWBG7ADRTFcZWd PMKdYiDPHV33YmCAg9tOAqV4O7TvaB07ZLKiI6kuSBtPVrazB8Az/oRJwfF6JQ6g 4ZdinyCrXWYrWslkW8402GKCERFFYJUvwLSUqHxYMRgZWPy9zf/mH56vh4bleYnP kz2X7OgtB3Juu0Uzwv927+KZuyzitniaPlLe9tsyBwXFbUM+BrY= =LWVf - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBXTpBq2aOgq3Tt24GAQhdwRAAnEMr6ZM17KlIUeytaKT5rNbGaXzDkKZR qp+9p5c6Zj5cblEDOBFgEIGUbX1zNCEQuK1RRCfK0S36cVaKMtEBACw5a8wa7oKE 4HIsWQaFDscuhtRy31+0RK07qN/9FGHEpc2Ddp+QbxZLaleBIJzEYaqpXobockFt vZ70TxyhBNptL/yJOERxixO3sDTUnXUiy832QwUTc8JQ6XCtcuj3cxg+5mxM2gAO gFsdTcHD6cOwsI7TeBjCrXFzc8JDr5kor6gj6SfI+u5mWG3bTB/jdVh62OT+7PrX dNQZ9VPwuRyKS18EkNYjWdDN+HjN8M3hOHRl+onlEOxxM/0IpLDxMp0JzHHVrN+T njyJQnSE5GOMhpB7z5S39JqZzBKO1DSeRojGnk+Hrn6joKZbMw92YlarVf9I1imv GDK/SXFYJjjl5t5jNNyCBxgsXniFZ/AxMnTrA+52RJ+onN5tPfBoAeobbtPt0jqI KtAuQnyeykow5SvviQ0KGU5ozsGTRnI2R0zdTdM8Rujl0frYESIsF8Zm4uCIbdR/ jOyCs0ZeaTkctbcdAMIjRk+EdmACQZ1bhfhrHJswggcLAjnaVKqGHfIo0yiWNy9X o/w+X3krDD4PHlHYMBbOH8HTd44fMXkHq4OKVRPANrPuJrBjaaoWSGaexBTaA5S8 i5rFvYOXOnI= =nH80 -----END PGP SIGNATURE-----