A vulnerability in the email message filtering feature of Cisco AsyncOS for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to cause an ESA device to become unavailable due to a denial of service (DoS) condition. The vulnerability is due to improper input validation when an email attachment contains corrupted fields and is filtered by the ESA. An attacker could exploit this vulnerability by sending a crafted email with an attachment to the ESA. A successful exploit could allow the attacker to cause a DoS condition. While the attachment is being filtered, memory is consumed at at high rate until the filtering process restarts. When the process restarts, it will resume processing the same malformed attachment and the DoS condition will continue. Cisco has released software updates that address this vulnerability. There are no workarounds that mitigate this vulnerability. This advisory is available at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151104-esa2
esa.prompt> filters detail all
Num Active Valid Names
1 Y Y example_filter
example_filter: if body-contains("example", 1) {
quarantine("Policy");
}
To determine whether a vulnerable version of Cisco AsyncOS Software is running on a Cisco ESA, administrators can use the version command in the ESA CLI. The following example shows the results for a device running Cisco AsyncOS Software version 8.5.3-051:
ciscoesa> version Current Version =============== Product: Cisco IronPort X1070 Messaging Gateway(tm) Appliance Model: X1070 Version: 8.5.3-051 . . .
esa> workqueue status
Failed to get work queue status: the queue is not mounted
AsyncOS for ESA Major Release | First Fixed Release for This Vulnerability | First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Companion Advisories |
---|---|---|
7.7 and prior |
Affected; migrate to 8.5.7-043 |
Affected; migrate to 8.5.7-043 or later |
8.0 or 8.0.1 |
Affected; migrate to 8.5.7-043 |
Affected; migrate to 8.5.7-043 or later |
8.0.2 | Affected; migrate to 9.1.1-023 |
Affected; migrate to 9.1.1-023 or later |
8.5 | 8.5.7-043 |
8.5.7-043 or later |
9.0 | Affected; migrate to 9.1.1-023 |
Affected; migrate to 9.1.1-023 or later |
9.1 | 9.1.1-023 | 9.1.1-023 or later |
9.5 | Affected; migrate to 9.6.0-046 | Affected; migrate to 9.6.0-046 or later |
9.6 | 9.6.0-046 | 9.6.0-046 or later |
9.7 | Not affected | Not affected |
In most cases an ESA can be updated over the network by using the System Upgrade options in the System Administration GUI. To upgrade a device by using the System Administration GUI:
After the upgrade is complete, the device reboots.
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 |
---|---|---|---|---|
1.2 | Added steps for upgrading a device by using the GUI. | Fixed Software | Final | 2015-November-20 |
1.1 | Added information about CES maintenance and upgrades. | Vulnerable Products | Final | 2015-November-16 |
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