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  • CERT Advisory CA-1998-10 Buffer Overflow in MIME-aware Mail and News Clients

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Original issue date: August 11, 1998
Last revised: October 19, 1998
Added vendor information for Compaq Computer Corporation

A complete revision history is at the end of this file.

The CERT Coordination Center has received reports of a vulnerability in some MIME-aware mail and news clients.

The CERT/CC team recommends updating any vulnerable mail or news clients according to the information provided in Appendix A. In addition, network administrators may be able to employ some risk mitigation strategies until they are able to update all the vulnerable clients. These strategies are described in Appendix B.

We will update this advisory as we receive additional information. Please check our advisory files regularly for updates that relate to your site.

As of the publication date of this advisory, we have not received any reports indicating this vulnerability has been successfully exploited.

I. Description

A vulnerability in some MIME-aware mail and news clients could allow an intruder to execute arbitrary code, crash the system, or gain administrative rights on vulnerable systems. The vulnerability has been discovered by Marko Laakso and Ari Takanen of the Secure Programming Group of the University of Oulu. It has received considerable public attention in the media and through reports published by Microsoft, Netscape, AUSCERT, CIAC, NTBugTraq, and others.

The vulnerability affects a number of mail and news clients in addition to the ones which have been the subjects of those reports.

II. Impact

An intruder who sends a carefully crafted mail message to a vulnerable system can, under some circumstances, cause code of the intruder's choosing to be executed on the vulnerable system. Additionally, an intruder can cause a vulnerable mail program to crash unexpectedly. Depending on the operating system on which the mail client is running and the privileges of the user running the vulnerable mail client, the intruder may be able to crash the entire system. If a privileged user reads mail with a vulnerable mail user agent, an intruder can gain administrative access to the system.

III. Solution

A. Obtain and install a patch for this problem as described in Appendix A.

B. Until you are able to install the appropriate patch, you may wish to install patches to sendmail or to use procmail filtering as described in Appendix B.

Appendix A - Vendor Information

Below is a list of the vendors who have provided information for this advisory. We will update this appendix as we receive additional information. If you do not see your vendor's name, the CERT/CC did not hear from that vendor. Please contact the vendor directly.

Caldera Inc.
Caldera is currently investigating these issues and in the process of releasing a fix. Updated RPMs will be uploaded to:
        9d2a8ca516c3bbbe920a72d365780fe3 mutt-0.93.1-2.i386.rpm
        a20383c9c6f73aac56731ab65c9525fd mutt-0.93.1-2.src.rpm

Compaq Computer Corporation

(c) Copyright 1994, 1995, 1996, 1997, 1998 Compaq Computer Corporation.
    All rights reserved.
SOURCE: Compaq Computer Corporation
        Compaq Services
        Software Security Response Team USA
        CIAC I-077,
        CERT CA-98.10
Subj.   mime-aware mail clients
    This reported problem is not present for the as shipped,
    Compaq's Digital ULTRIX or Compaq's Digital UNIX
    Operating Systems Software.
                                 - Compaq Computer Corporation

Data General Corporation

DG/UX is not vulnerable to this report as it includes no native utilities with mime support.


Fujitsu's operating system, UXP/V, does not support any mail client which can handle MIME encoding/decoding. Therefore, Fujitsu UXP/V is not vulnerable.

Hewlett-Packard Company

The version of dtmail supplied by HP, as part of HP's CDE product, is vulnerable. Patches in process.


Iris is aware of this problem and is investigating to determine if Lotus Notes is vulnerable.

Microsoft Corporation

Previously released information regarding this vulnerability is available from Microsoft at


Mutt versions up to 0.93.1(i) were vulnerable to a remotely exploitable buffer overflow. The bug has been fixed as of mutt 0.93.2(i). A patch was distributed on Usenet on July 29.

Users of older versions should upgrade as soon as possible.

 Mutt 0.93.2(i) is available from

The distribution files with their MD5 checksums:

diff-0.93.1-0.93.2.gz 39918e8c27e1a762af77052ea1164dbb
diff-0.93.1i-0.93.2i.gz aa08b3b3ade6e733c9bb01809199e3e7
mutt-0.93.2i.tar.gz 9ce8f1020a638d07cb3772b1ebe9887d
mutt-0.93.2.tar.gz 89a0888b1d25895cdc74f0999713f52b

SHA1 checksums:

diff-0.93.1-0.93.2.gz 326b4dd8479717ab1bc073a1a3eaa13ef6d551df
diff-0.93.1i-0.93.2i.gz 1358d1462d76c1c41a2070bdf5eee1b60a216ee8
mutt-0.93.2i.tar.gz 2a16bd1ee9edf24222d39998e80d8adafa6d45fa
mutt-0.93.2.tar.gz 1048f600395b328783bf58dedddd9a18ad4e36d1

Credits for noting this bug and giving a first fix on bugtraq go to Paul Boehm <>.


No products are affected.

NetBSD Foundation

The NetBSD Foundation package system contains packages for mutt and pine. All users should upgrade to the latest version of these packages as soon as possible. Updated binary packages will become available on the NetBSD FTP server as soon as possible, and will be announced on the list. To join this list, or more information about NetBSD, please see http://www.NetBSD.ORG/


Previously released information regarding this vulnerability is available from Netscape at


Not affected. OpenBSD does not ship any of the affected products.

Pegasus Mail

We have conducted a strenuous examination of the equivalent code in Pegasus Mail and can confirm that Pegasus Mail is *not* vulnerable to this particular attack. Pegasus Mail handles attachments in a different manner from the affected Netscape and Microsoft products, and does proper bounds checking on filename lengths in all cases.

In the course of following up on this problem, we *have* unearthed a related problem, though: there are conceivable scenarios where Pegasus Mail may be made to crash when it attempts to parse a particular class of improperly-formatted MIME headers. The crash does not result from a buffer overflow, and hence has none of the security ramifications of the Netscape/OE problem - the crash itself is the worst that can happen. We have corrected this particular parser problem for the v3.01c release of Pegasus Mail, which will be out early next week.

To reiterate: Pegasus Mail is *not* vulnerable to the problem currently being publicized.

Mercury users: our Mercury Mail Transport System is not currently required to perform MIME parsing, and is hence completely immune to this problem.

QUALCOMM Incorporated

Eudora Pro Email, Eudora Pro CommCenter and Eudora Light not susceptible to buffer overflow security problem

QUALCOMM tested its line of Eudora email software after becoming aware of the buffer overflow security problems recently found in Microsoft and Netscape email programs. QUALCOMM is pleased to announce that its Eudora email products are not susceptible to the types of attacks that can harm the computers of users of these other products. QUALCOMM tested the latest versions of Eudora Pro and Eudora CommCenter versions 4.0, 4.0.1 and 4.1 (beta), as well as Eudora Pro and Eudora Light versions 3.0 through 3.0.5 (Windows) and 3.1.3 (Mac). In all cases, Eudora does not allow any unauthorized programs to be automatically executed on a user's system by exploiting buffer overflow flaws.

Internally, Eudora 4.0.1 (shipping) and 4.1 (beta) checks incoming header sizes and in particular attachment name lengths and truncates where appropriate to avoid buffer overrun. Previous versions of Eudora, specifically the Windows Eudora versions 3.0 through 3.0.5 and 4.0, long attachment names under certain conditions could cause the program to terminate prematurely, but most importantly, not in such a way as to allow unauthorized execution of code. Upgrading to Windows Eudora 4.0.1 or 4.0.2 (both shipping) or 4.1 (beta) resolves that particular issue.

An unrelated security issue has recently been made public regarding the use of Java scripts and attachments in email messages received by Eudora 4.x. Full details of this issue, along with links to Eudora Pro 4.0.2 and 4.1 updaters is available at  The available Eudora Pro 4.0.2 and 4.1 updaters correct the potential security risk.

The Santa Cruz Operation, Inc. (SCO)

The following SCO products are not vulnerable:
    - - SCO CMW+
    - - SCO Open Desktop / Open Server 3.0, SCO UNIX 3.2v4
    - - SCO OpenServer 5, SCO Internet FastStart
    - - SCO UnixWare 2.1

SCO UnixWare 7 dtmail may be vulnerable - investigation is continuing. Pending this investigation, SCO recommends that dtmail not be used on UnixWare 7; mail may be safely read using mailx or Netscape Navigator.

Sun Microsystems, Inc.

Please refer to Sun Microsystems, Inc. Security Bulletin, "mailtool", Number: 00175, distributed September 9, 1998 for additional information relating to this vulnerability.

Patches and Checksums are available to all Sun customers via World Wide Web at:

Sun security bulletins are available via World Wide Web at:

University of Washington

Pursuant to recent reports of vulnerability to mal-formed or malicious MIME attachments, the UW Pine Team has corrected a few cases of potential buffer overrun in the latest Pine Message System release, version 4.02, that might cause Pine to crash when inordinately long MIME-header information is encountered.

It has been speculated that these problems could be exploited to allow a message sender to execute an arbitrary command on behalf of the receiving user, although with no more privilege than the receiving user. While the UW Pine Team is not aware of any specific attacks involving this bug, they have made a source patch available to address this threat.

The source patch is available from:

Or via links found within the Pine Information Center at:

The patch is intended for the Pine Mail System version 4.02 (released 21 July 1998). The file is in context-diff format, and should be understood by the "patch" utility. To update Pine 4.02 source, simply copy the patch file into the same directory as the pine4.02 source tree and type:

    patch -p < pine4.02A.patch

The UW Pine Team strongly encourages sites running version 4.00 or greater to upgrade to the latest release, and apply the published patch. While versions prior to 4.00 are less sensitive to malicious messages, upgrading to version 4.02A (including the patch) is recommended.

Appendix B - Risk Mitigation 

Although the vulnerability described in this advisory affects mail user agents, it may be possible to reduce the risk by modifying mail transfer agents to detect the vulnerability before it reaches the mail user agent, or by filtering the message. Below is a list of vendors who have provided us information on strategies that can mitigate the risk. Note that these vendors are not themselves vulnerable to this problem.

Sendmail, Inc.

Sendmail, Inc. has produced a patch for version 8.9.1 of sendmail as a service to their user base to assist system administrators in proactively defending against these problems. Sites who choose not to install the patch at this time will not increase their exposure to the problem in this case. This patch and installation instructions are available at

Note that the patch is specific to sendmail version 8.9.1 only. If you are unable to upgrade to this version, do not attempt to use the patch.

John Hardin

John Hardin has modified his procmail Filters Kit to include filters which may be able to assist sites in defending against these problems. More information about the procmail Filters Kit is available at

Our thanks go to Marko Laakso and Ari Takanen of the Secure Programming Group of the University of Oulu; Eric Allman and Gregory Shapiro of Sendmail, Inc; AUSCERT; DFN-CERT; John Hardin; and Gene Spafford of Purdue University for their input.

Any material furnished by Carnegie Mellon University and the Software Engineering Institute is furnished on an "as is" basis. Carnegie Mellon University makes no warranties of any kind, either expressed or implied as to any matter including, but not limited to, warranty of fitness for a particular purpose or merchantability, exclusivity or results obtained from use of the material. Carnegie Mellon University does not make any warranty of any kind with respect to freedom from patent, trademark, or copyright infringement.

Copyright 1998 Carnegie Mellon University.

Revision History
Oct. 19, 1998  Added vendor information for Compaq Computer Corporation
Sept. 18, 1998 Added vendor information for Sun Microsystems, Inc.
Aug. 12, 1998  Added vendor information, see Appendix A
	       Updated risk mitigation information, see Appendix B
Aug. 11, 1998  Updated vendor information for Pegasus Mail
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