Public Vulnerability Reports

Microsoft Multiple E-Mail Client Address Spoofing Vulnerability



Microsoft Outlook provides an integrated solution for managing and
organizing e-mail messages, schedules, tasks, notes, contacts, and other
information. More information is available at


Remote exploitation of an address spoofing vulnerability in various
Microsoft Corp. e-mail clients could allow attackers to social engineer
sensitive information from end users.

Microsoft Outlook and Microsoft Outlook Web Access (OWA) are widely
deployed collaboration clients in corporate networks. The vulnerability
specifically exists in message header parsing and allows an attacker to
spoof the "From" field that is displayed on the user's screen. Within
the SMTP header, when the From field contains multiple comma-separated
addresses, Outlook and OWA will only display the first address. Consider
the following example header:

    From:, Phisher <phisher@attackers.domain>

Outlook and OWA will only display the address "" as
the sender address.


While server-side e-mail spoofing is a known matter, this issue is
relevant as it exists within the client. Consider the following example:
A corporate SMTP server is configured to drop all mail received from the
external network claiming to be from an internal address. By exploiting
this issue, an attacker can bypass the imposed restrictions and transmit
a message that appears to come from an internal user. This attack,
combined with social engineering, could potentially lead to further


Microsoft Outlook as distributed with Office XP and 2003 as well as
Outlook Web Access as distributed with Exchange 2003 have been confirmed
as vulnerable. Prior versions are suspected to be affected as well.

Microsoft Outlook Express is not affected by this issue.


Examine the full mail headers of any suspicious e-mail messages prior to
taking described actions or following live links.


Microsoft has reviewed the issue and has made the determination that
while a bug fix may be implemented in a future service pack, a security
advisory/patch will not be released for this issue.


 The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-1052 to these issues. This is a candidate for inclusion
in the CVE list (, which standardizes names for
security problems.


01/21/2005   Initial vendor notification
01/24/2005   Initial vendor response
04/08/2005   Public disclosure


This vulnerability was discovered by Sergey V. Gordeychik.

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Copyright © 2005 Verisign, Inc.

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