Cisco Security Advisory
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CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N/E:X/RL:X/RC:X
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A vulnerability in the Multipurpose Internet Mail Extensions (MIME) scanner of Cisco AsyncOS Software for Cisco Email Security Appliances (ESA) could allow an unauthenticated, remote attacker to bypass configured user filters on the device.
The vulnerability is due to improper error handling of a malformed MIME header in an email attachment. An attacker could exploit this vulnerability by sending an email with a crafted MIME attachment. For example, a successful exploit could allow the attacker to bypass user filters configured to prevent executable files from being opened. The malformed MIME headers may not be RFC compliant but some mail clients could still allow users to access the attachment, which may not have been properly filtered by the device.
There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170215-asyncos
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Vulnerable Products
This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for Cisco ESA, both virtual and hardware appliances, that are configured with message or content filters to scan incoming email attachments on the ESA.Products Confirmed Not Vulnerable
No other Cisco products are currently known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect Cisco Web Security Appliances or Content Security Management Appliance, virtual and hardware versions.
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There are no workarounds that address this vulnerability.
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For information about fixed software releases, consult the Cisco bug ID(s) at the top of this advisory.
When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts page, to determine exposure and a complete upgrade solution.
In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
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The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
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Cisco would like to thank security researcher Martin Ervius for reporting this vulnerability.
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To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
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Show LessVersion Description Section Status Date 1.3 Removed the Cisco Web Security Appliances (WSA) as a product affected by this vulnerability. Summary, Affected Products Final 2017-May-11 1.2 Removed the Details Section on the malformed-header configuration option. Details Final 2017-February-28 1.1 Added information about the malformed-header rule. Details Final 2017-February-23 1.0 Initial public release. — Final 2017-February-15
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