Microsoft Vulnerability Research Advisory MSVR12-012

Safari Content-Disposition Handling Could Allow Cross-site Scripting

Published: August 21, 2012

Version: 1.0

Overview

Executive Summary

Microsoft is providing notification of the discovery and remediation of a vulnerability affecting Apple Safari software version 5.1.5 (7534.55.3) for Windows and earlier. Microsoft discovered and disclosed the vulnerability under coordinated vulnerability disclosure to the affected vendor, Apple. Apple has remediated the vulnerability in their software.

The vulnerability exists in the way that Apple Safari handles files with the content disposition header set to 'attachment'. When a file with this value set is opened within the browser any script within the file could be executed inline.

Microsoft Vulnerability Research reported this issue to and coordinated with Apple to ensure remediation of this issue. The vulnerability has been assigned the entry, CVE-2011-3426, in the Common Vulnerabilities and Exposures list. For more information, including information about updates from Apple, see Apple security updates.

Mitigating Factors

• An attacker must convince a victim to click a specially crafted URL or to access a file on a website through Safari, for example by opening an attachment in a web-based email application.

Advisory Details

Purpose and Recommendation

Purpose of Advisory: To notify users of a vulnerability and its remediation.

Advisory Status: Advisory published.

Recommendation: Review the Suggested Actions section and configure as appropriate.

Issue References

For more information about this issue, see the following references:

Affected and Non-Affected Software

This advisory discusses the following software:

Frequently Asked Questions

What is the scope of this advisory?
This advisory is part of a coordinated release with affected vendors to inform customers of a security issue that may affect their systems.

Is this a security vulnerability that requires Microsoft to issue a security update?
No. This vulnerability has been fixed via an update from the affected third-party vendors. The update remediates the software listed in the table, Affected Software.

What is the scope of the vulnerability?
This is a cross-site scripting vulnerability that could lead to execution of arbitrary code in the context of the user on the server.

What causes the vulnerability?
This issue is caused by the way Safari interprets the 'attachment' value for the HTTP Content-Disposition header. A script within any file using the 'attachment' value would be served inline and executed.

What might an attacker use this vulnerability to do?
An attacker leveraging this vulnerability would be able to execute a script with the credentials of the logged on user.

How could an attacker exploit the vulnerability?
An attacker could leverage this issue by convincing a user to click on a specially crafted URL or by accessing a file on a website through Safari.

Suggested Actions

Upgrade to the latest version of Apple Safari.

Other Information

Acknowledgments

Microsoft thanks the following:

• Hidetake Jo of Microsoft and Apple for working toward a resolution

Disclaimer

The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions

• V1.0 (August 21, 2012): Advisory published.

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