Cisco Security Advisory
Cisco Email Security Appliance Malformed EML Attachment Bypass Vulnerability
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CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N/E:X/RL:X/RC:X
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A vulnerability in the malware detection functionality within Advanced Malware Protection (AMP) of Cisco AsyncOS Software for Cisco Email Security Appliances (ESAs) could allow an unauthenticated, remote attacker to cause an email attachment containing malware to be delivered to the end user.
The vulnerability is due to the failure of AMP to scan certain EML attachments that could contain malware. An attacker could exploit this vulnerability by sending an email with a crafted EML attachment through the targeted device. A successful exploit could allow the attacker to bypass the configured ESA email message and content filtering and allow the malware to be delivered to the end user.
There are workarounds that address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170906-esa
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Vulnerable Products
This vulnerability affects 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. For information about affected software releases, consult the Cisco bug ID(s) at the top of this advisory.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 the following products:
- Cisco Web Security Appliance, virtual and hardware versions
- Cisco Content Security Management Appliance, virtual and hardware versions
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The ESA should be configured for multiple levels of email attachment scanning to ensure that a corrupted EML attachment is scanned by multiple packages with the ESA.
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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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This vulnerability was found during resolution of a Cisco TAC Support case.
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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 1.1 Added a workaround. Summary and Workaround Final 2017-September-18 1.0 Initial public release. - Final 2017-September-06
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