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AUSCERT External Security Bulletin Redistribution
ESB-2006.0641 -- [Win]
IBM Lotus Notes File Viewer Overflow Vulnerability (dunzip32.dll)
7 September 2006
AusCERT Security Bulletin Summary
Product: Lotus Notes 6.5x clients
Operating System: Windows
Impact: Execute Arbitrary Code/Commands
Denial of Service
Comment: This ESB describes a vulnerability in a third party library
(DUNZIP32.dll) which may be present in products other than Lotus
Notes. More information can be found from the US-CERT
vulnerability note VU#582498:
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IBM Lotus Notes File Viewer Overflow Vulnerability (dunzip32.dll)
CERT and Juha-Matti Laurio each independently contacted IBM Lotus to
report a buffer overflow vulnerability in the InnerMedia DynaZip
library used in Lotus Notes 6.5x clients that run on Microsoft Windows
To successfully exploit these issues, an attacker would need to send a
specially crafted file attachment to users via email, and the users
would have to double-click and "View" the attachment. This issue
applies to zip file attachments only. If successfully exploited, this
vulnerability will cause the Notes client to crash and may allow
execution of arbitrary code.
This issue has been documented by the following advisories:
CERT VU# 582498:
Networksecurity.fi Security Advisory:
This issue was reported to IBM Lotus Quality Engineering as SPR#
KSPR67MNMU and addressed in Notes 6.5.5 and Notes 7.0.
Refer to the Upgrade Central site for details on upgrading
Notes/Domino to these releases.
Workaround if 6.5.5 DLL is available:
The buffer overflow vulnerability affects the dunzip32.dll file. This
dll file has been updated in the fixed releases. If you cannot
immediately upgrade the Notes client in your environment, then it is
possible to correct the issue by copying the revised version of the
dunzip32.dll file from a 6.5.5 release over the version found in
earlier 6.x releases.
Workaround if 6.5.5 is not available:
To work around this issue in previous releases of Notes, the affected
file viewer can be disabled by either commenting out the relative
dll's in the keyview.ini file found in the program directory or by
deleting the files from the program directory.
There are three options for disabling this viewer:
1. Delete the keyview.ini file in the Notes program directory. This
disables ALL viewers. When a user clicks View (for any file), a dialog
box will be displayed with the message "Unable to locate the viewer
2. Delete the problem file (dunzip32.dll). When a user tries to view
the specific file types (zip archives), a dialog box will be displayed
with the message "The viewer display window could not be initialized."
All other file types work without returning the error message.
3. Set the ViewerConfigFile to an invalid file name using a policy.
This can be done by adding a field to your Desktop Settings policy
with the name $PrefViewerConfigFile and set it to an invalid file.
Note that if an administrator chooses to set the ViewerConfigFile to
an invalid file name, they will get the same result as Option1 above.
When a user clicks View (for any file), a dialog box will be displayed
with the message "Unable to locate the viewer configuration file."
This disables ALL viewers.
General instructions on how to distribute notes.ini parameters via
policies have been published in the Domino 7 Administrator's Help
Guide under the topic "Using policies to assign NOTES.INI or Location
document settings to Notes client users."
To use a policy to assign a NOTES.INI value to Notes client users, use
the Domino Designer to add a new field to the Desktop Policy Settings
document. The new field must be named $PrefVariableName, where
VariableName is the name of the NOTES.INI variable you want to set. In
the new field on the Desktop Policy Settings document, enter the value
you want assigned to that NOTES.INI variable. That is the value that
is set in the NOTES.INI for the assigned Notes users.
To push a notes.ini parameter down via a Desktop policy, perform the
a. From the Domino Designer, open the desktop policy settings
b. Create a new field named $PrefViewerConfigFile.
c. Assign the default value to the field $PrefViewerConfigFile to an
invalid file name.
d. Save and exit.
e. Create a Desktop Settings document as you normally would.
f. Create a Policy document for your users and select the Desktop
settings document created in Step 5. Save and close the Policy
g. If you created an explicit policy, assign it to your users.
h. When the Notes clients authenticate with the server, the notes.ini
parameter should be pushed down. (Be aware that the Notes client
dynamic configuration (DCC) must run and it may take until the
next day for this setting to take effect).
In general, users are strongly urged to use caution when opening or
viewing unsolicited file attachments.
The attachment(s) will not auto-execute upon opening or previewing the
email message; the file attachment must be opened by the user using
the affected file viewer (from the menu bar, select "Attachment", then
This affects the Notes client on Microsoft Windows operating systems
only. The Domino server is not affected by this issue.
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