A vulnerability in the proxy cache functionality of Cisco AsyncOS for Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition because the device runs out of system memory. The vulnerability is due to improper memory operations by the affected software. The software fails to free a memory object when it retrieves data from the proxy server cache to terminate a TCP connection. An attacker could exploit this vulnerability by opening many proxy connections through the WSA. An exploit could allow the attacker to cause the WSA to stop passing traffic when enough memory is leaked. Cisco has released software updates that address this vulnerability. A workaround that mitigates this vulnerability is also available. This advisory is available at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151104-wsa1
To determine whether a vulnerable version of Cisco AsyncOS Software is running on a Cisco WSA, administrators can use the version command in the WSA CLI. The following example shows the results for an appliance running Cisco AsyncOS Software version 8.5.3-051:
ciscowsa> version
Current Version
===============
Product: Cisco IronPort S670 Web Security Appliance
Model: S670
Version: 8.5.3-051 . . .
# status detail Connections: Total client connections 99999
| AsyncOS for WSA Major Release |
First Fixed Release for This Vulnerability |
First Fixed Release for This Vulnerability and All Vulnerabilities Described in the Companion Advisories |
|---|---|---|
| 7.5 and prior | Not affected |
7.7.0-761 or later |
| 7.7 |
Not affected |
7.7.0-761 or later |
| 8.0 | 8.0.7-151 | 8.0.8-113 or later |
| 8.1 | Affected; migrate to 8.5.2-004 | Affected; migrate to 8.5.3-051 or later |
| 8.5 | 8.5.2-004 | 8.5.3-051 or later |
| 8.6 | Affected; migrate to 8.7.0-171-LD | Affected; migrate to 8.7.0-171-LD or later |
| 8.7 | 8.7.0-171-LD | 8.7.0-171-LD or later |
| 8.8 | 8.8.0-085 | 8.8.0-085 or later |
| 9.0 | Not affected | Not affected |
In most cases a WSA 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 |
|---|---|---|---|---|
| 1.1 | Added steps for upgrading a device by using the GUI. | Fixed Software | Final | 2015-November-20 |
| 1.0 | Initial public release. | - | Final | 2015-November-04 |
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