A vulnerability in the email message filtering feature of Cisco AsyncOS Software for the Cisco Email Security Appliance could allow an unauthenticated, remote attacker to cause an affected device to run out of memory and stop scanning and forwarding email messages. When system memory is depleted, it can cause the filtering process to crash, resulting in a denial of service (DoS) condition on the device. The vulnerability is due to improper input validation of email attachments that contain corrupted fields. An attacker could exploit this vulnerability by sending an email message with an attachment that contains corrupted fields through a targeted device. When the affected software filters the attachment, the filtering process could crash when the system runs out of memory and the process restarts, resulting in a DoS condition. After the filtering process restarts, the software resumes filtering for the same attachment, causing the filtering process to crash and restart again. A successful exploit 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://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170920-esa
This vulnerability affects software version 9.0 through 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 or content filter to incoming email attachments. The vulnerability is not limited to any specific rules or actions for a message filter or content filter.
To determine which message filters are configured for a Cisco Email Security Appliance (ESA), administrators can use the filters detail all command in the CLI. The following example shows the output of the filters detail all command for an ESA that is configured to use a generic message filter:esa.prompt> filters detail allTo determine which content filters are configured for an ESA, administrators can use the policyconfig command in the CLI or the Cisco AsyncOS System Administration GUI. In the System Administration GUI, do the following:
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: 9.7.2-065
Note that Cisco provides regular maintenance of products in the Cisco Cloud Email Security (CES) service solution, which includes Cisco Email Security Appliances and Cisco Content Security Management Appliances. Customers can also request a software upgrade by contacting Cisco CES support.
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 upgrade 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 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
In the following table, the left column lists major releases of Cisco AsyncOS Software for ESA. The right column indicates whether a major release is affected by the vulnerability described in this advisory and the first minor release that includes the fix for this vulnerability.
Customers should upgrade to an appropriate release as indicated in the following table:
| Cisco AsyncOS ESA Software Major Release | First Fixed Release for This Vulnerability |
|---|---|
| Prior to 8.5 | Not Vulnerable |
| 8.5 | Not Vulnerable |
| 9.0 |
Affected; migrate to 9.8.1 or 10.0.2-20 or later |
| 9.1 | Affected; migrate to 9.8.1 or 10.0.2-20 or later |
| 9.5 | Affected; migrate to 9.8.1 or 10.0.2-20 or later |
| 9.6 | Affected; migrate to 9.8.1 or 10.0.2-20 or later |
| 9.7 | Affected; migrate to 9.8.1 or 10.0.2-20 or later |
| 9.8 |
9.8.1 |
| 10.0 | 10.0.2-020 |
| 11.0 | Not Vulnerable |
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.
This vulnerability was found during internal security testing.
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.
| Version | Description | Section | Status | Date |
|---|---|---|---|---|
| 1.0 | Initial public release. | - | Final | 2017-September-20 |
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