From security-officer@FreeBSD.ORG Thu Mar 30 04:35:36 2000 From: FreeBSD Security Officer , FreeBSD Security Officer Resent-From: mea culpa To: undisclosed-recipients: ; Resent-To: jericho@attrition.org Date: Sun, 19 Mar 2000 22:31:45 -0800 (PST) Reply-To: postmaster@FreeBSD.ORG Subject: FreeBSD Security Advisory: FreeBSD-SA-00:07.mh [REVISED] -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-00:07 Security Advisory FreeBSD, Inc. Topic: mh/nmh/exmh/exmh2 ports allow remote execution of binary code Category: ports Module: mh/nmh/exmh/exmh2 Announced: 2000-03-15 Revised: 2000-03-19 Affects: Ports collection before the correction date. Corrected: [See below for a more complete description] All versions fixed in 4.0-RELEASE. mh: 2000-03-04 nmh: 2000-02-29 exmh: 2000-03-05 exmh2: 2000-03-05 FreeBSD only: NO I. Background MH and its successor NMH are popular Mail User Agents. EXMH and EXMH2 are TCL/TK-based front-ends to the MH system. There are also Japanese-language versions of the MH and EXMH2 ports, but these are developed separately and are not vulnerable to the problem described here. II. Problem Description The mhshow command used for viewing MIME attachments contains a buffer overflow which can be exploited by a specially-crafted email attachment, which will allow the execution of arbitrary code as the local user when the attachment is opened. The *MH ports are not installed by default, nor are they "part of FreeBSD" as such: they are part of the FreeBSD ports collection, which contains over 3100 third-party applications in a ready-to-install format. The FreeBSD 4.0-RELEASE ports collection is not vulnerable to this problem. FreeBSD makes no claim about the security of these third-party applications, although an effort is underway to provide a security audit of the most security-critical ports. III. Impact An attacker who can convince a user to open a hostile MIME attachment sent as part of an email message can execute arbitrary binary code running with the privileges of that user. If you have not chosen to install any of the mh/nmh/exmh/exmh2 ports/packages, then your system is not vulnerable. The Japanese-language version of MH is being actively developed and is believed to have fixed this particular problem over a year ago. Consequently the ja-mh and ja-exmh2 ports are not believed to be vulnerable to this problem. IV. Workaround 1) Remove the mhshow binary, located in /usr/local/bin/mhshow. This will prevent the viewing of MIME attachments from within *mh. 2) Remove the mh/nmh/exmh/exmh2 ports, if you you have installed them. V. Solution The English language version of the MH software is no longer actively developed, and no fix is currently available. It is unknown whether a fix to the problem will be forthcoming - consider upgrading to use NMH instead, which is the designated successor of the MH software. EXMH and EXMH2 can both be compiled to use NMH instead (this is now the default behaviour). It is not necessary to recompile EXMH/EXMH2 after reinstalling NMH. SOLUTION: Remove any old versions of the mail/mh or mail/nmh ports and perform one of the following: 1) Upgrade your entire ports collection and rebuild the mail/nmh port. 2) Reinstall a new package obtained from: ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/mail/nmh-1.0.3.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-current/mail/nmh-1.0.3.tgz ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-current/mail/nmh-1.0.3.tgz 3) download a new port skeleton for the nmh port from: http://www.freebsd.org/ports/ and use it to rebuild the port. 4) Use the portcheckout utility to automate option (3) above. The portcheckout port is available in /usr/ports/devel/portcheckout or the package can be obtained from: ftp://ftp.freebsd.org/pub/FreeBSD/ports/packages/devel/portcheckout-1.0.tgz VI. Revision history v1.0 2000-03-15 Initial release v1.1 2000-03-19 Update to note that the japanese-localized ports are not vulnerable -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBONXFXlUuHi5z0oilAQHQ/QP9FCTFiFlaeSv2ROM46PbDkF6MN39SLTuv DEW6a6wmMU5+YbSTlFLjvYrqYgpjOmM7NMOMhhceVVpoZVMMPonHuJxHWh7YvF2G T4bZcRM3kpRcjXAOQnIiUrgh77zoEmfBysAmHZbNucCmOB5y7UqHI3CM31+geiPR /bsvHCy4U0U= =Odcg -----END PGP SIGNATURE----- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security-notifications" in the body of the message