A vulnerability in the anti-spam scanner of Cisco AsyncOS for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the anti-spam functionality of the ESA. The vulnerability is due to improper error handling of a malformed packet in the anti-spam scanner. An attacker could exploit this vulnerability by sending a crafted DNS Sender Policy Framework (SPF) text record. A successful exploit could allow the attacker to bypass the anti-spam scanner and generate a malformed packet alert. 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-20150612-esa
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 . . .
CriticalTo view the error logs, use the mail_logs command in the ESA CLI. The mail_logs log file contains the most recent system log messages.: MID ###### cannot be scanned by IMS. The message is either malformed or bad headers.
Warning: case antispam - engine (44476) : case-daemon: bdecode error: bad format: pos 921, ...
esa> mail_logs
esa> grep "The message is either malformed or bad headers" mail_logs
| 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 |
|---|---|---|
| 7.6 and prior |
7.6.3-027 | Affected; migrate to 8.5.7-043 or later |
| 8.0 and 8.0.1 |
8.5.7-043 |
Affected; migrate to 8.5.7-043 or later |
| 8.0.2 | 8.0.2-055 |
Affected; migrate to 9.1.1-023 or later |
| 8.5 | 8.5.7-043 | 8.5.7-043 or later |
| 9.0 | 9.1.0-032 | Affected; migrate to 9.1.1-023 or later |
| 9.1 | 9.1.1-023 |
9.1.1-023 or later |
| 9.5 | 9.5.0-201 | Affected; migrate to 9.6.0-046 or later |
| 9.6 | 9.6.0-042 | 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 |
|---|---|---|---|---|
| 2.2 | Added steps for upgrading a device by using the GUI. | Fixed Software | Final | 2015-November-20 |
| 2.1 | Added information about CES maintenance and upgrades. | Vulnerable Products | Final | 2015-November-16 |
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