AV:N/AC:L/Au:N/C:N/I:N/A:C/E:F/RL:OF/RC:C
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A vulnerability in the email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliances could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
The vulnerability exists because the message filtering feature of the affected software does not properly validate compressed message attachments that contain malformed Design (DGN) files. An attacker could exploit this vulnerability by sending a crafted email message, which has a compressed attachment containing a malformed DGN file, through an affected device. While the affected software filters the attachment, memory could be consumed at a high rate and ultimately exhausted, causing the filtering process to restart and resulting in a DoS condition. After the filtering process restarts, the software resumes filtering for the same attachment, causing the filtering process to exhaust memory and restart again. A successful exploit of this vulnerability could allow the attacker to cause a repeated DoS condition.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161026-esa1
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Vulnerable Products
This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for Cisco Email Security Appliances, both virtual and hardware appliances, if the software is configured to apply a message filter that contains any of the following rules:
- body-contains
- attachment-contains
- every-attachment-contains
- attachment-binary-contains
- dictionary-match
- attachment-dictionary-match
esa.prompt> filters detail all Num Active Valid Names 1 Y Y example_filter example_filter: if body-contains("example", 1) { quarantine("Policy"); }
ciscoesa> version Current Version =============== Product: Cisco IronPort X1070 Messaging Gateway(tm) Appliance Model: X1070 Version: 8.5.7-044 . . .
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 Content Security Management Appliance, virtual and hardware versions
- Cisco Web Security Appliance, virtual and hardware versions
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There are no workarounds that address this vulnerability.
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Cisco has released free software updates that address the vulnerability described in this advisory. Customers may only install and expect support for software versions and feature sets for which they have purchased a license. By installing, downloading, accessing, or otherwise using such software upgrades, customers agree to follow the terms of the Cisco software license:
http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html
Additionally, customers may only download software for which they have a valid license, procured from Cisco directly, or through a Cisco authorized reseller or partner. In most cases this will be a maintenance upgrade to software that was previously purchased. Free security software updates do not entitle customers to a new software license, additional software feature sets, or major revision upgrades.
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.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco Technical Assistance Center (TAC):
http://www.cisco.com/en/US/support/tsd_cisco_worldwide_contacts.html
Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.
Fixed Releases
Customers should upgrade to an appropriate release as indicated in this section. To help ensure a complete upgrade solution, consider that this advisory is part of a collection that includes the following advisories:- cisco-sa-20161026-esa1: Cisco Email Security Appliance Malformed DGN File Attachment Denial of Service Vulnerability
- cisco-sa-20161026-esa2: Cisco Email Security Appliance Advanced Malware Protection Attachment Scanning Denial of Service Vulnerability
- cisco-sa-20161026-esa3: Cisco Email Security Appliance Corrupted Attachment Fields Denial of Service Vulnerability
Customers should upgrade to an appropriate release as indicated in the following table:
Cisco AsyncOS Software Major Release First Fixed Release for This Vulnerability Recommended Release for All Vulnerabilities Described in the Collection of Advisories Prior to 8.0
Affected; migrate to 9.1.1-038
9.1.2-041
8.0
Affected; migrate to 9.1.1-038
9.1.2-041
8.5 Affected; migrate to 9.1.1-038
9.1.2-041 9.0 Affected; migrate to 9.1.1-038
9.1.2-041 9.1 Affected; migrate to 9.1.1-038 9.1.2-041 9.5 Affected; migrate to 9.7.1-066 9.7.2-065 9.6 Affected; migrate to 9.7.1-066
9.7.2-065 9.7 Affected; migrate to 9.7.1-066 9.7.2-065 10.0 Affected; migrate to 10.0.0-124
10.0.0-203
Note: In the preceding table, the recommended release also includes the fix for a critical vulnerability that was recently disclosed for Cisco AsyncOS Software releases 9.1.2 through 10.0.0. For more information, see the Cisco Email Security Appliance Internal Testing Interface Vulnerability security advisory.
In most cases, administrators can upgrade ESA software over the network by doing the following in the Cisco AsyncOS System Administration GUI:
- Choose System Administration > System Upgrade.
- Click Upgrade Options.
- Click Download.
- Choose the Cisco AsyncOS Software release to upgrade to.
- In the Upgrade Preparation area, choose the appropriate options.
- To begin the upgrade, click Proceed. A progress bar displays the status of the upgrade.
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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 the resolution of a 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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Version Description Section Status Date 1.0 Initial public release. — Final 2016-October-26
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