Summary
A vulnerability in the content scanning and message filtering features of Cisco Secure Email Gateway could allow an unauthenticated, remote attacker to overwrite arbitrary files on the underlying operating system.
This vulnerability is due to improper handling of email attachments when file analysis and content filters are enabled. An attacker could exploit this vulnerability by sending an email that contains a crafted attachment through an affected device. A successful exploit could allow the attacker to replace any file on the underlying file system. The attacker could then perform any of the following actions: add users with root privileges, modify the device configuration, execute arbitrary code, or cause a permanent denial of service (DoS) condition on the affected device.
Note: Manual intervention is required to recover from the DoS condition. Customers are advised to contact the Cisco Technical Assistance Center (TAC) to help recover a device in this condition.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
Affected Products
Vulnerable Products
This vulnerability affects Cisco Secure Email Gateway if it is running a vulnerable release of Cisco AsyncOS and both of the following conditions are met:
- Either the file analysis feature, which is part of Cisco Advanced Malware Protection (AMP), or the content filter feature is enabled and assigned to an incoming mail policy
- The Content Scanner Tools version is earlier than 23.3.0.4823
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Determine Whether File Analysis is Enabled
To determine whether file analysis is enabled, complete the following steps:
- Connect to the product web management interface.
- Choose Mail Policies > Incoming Mail Policies > Advanced Malware Protection.
- Choose a Mail Policy and inspect the value of Enable File Analysis.
If the box is checked, file analysis is enabled.
Determine Whether Content Filters are Enabled
To determine whether content filters are enabled, complete the following steps:
- Connect to the product web interface.
- Choose Mail Policies > Incoming Mail Policies > Content Filters.
If the Content Filters column contains anything other than Disabled, content filters are enabled.
Determine the Content Scanner Tools Version
To determine which version of Content Scanner is running, use the contentscannerstatus CLI command. The following example shows a vulnerable version of Content Scanner Tools:
cisco-esa> contentscannerstatus
Component Version Last Updated
Content Scanner Tools 23.1.0.4619.13.0.1500022 Never updated
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following Cisco products:
- Secure Email and Web Manager
- Secure Web Appliance
Workarounds
- There are no workarounds that address this vulnerability.
Fixed Software
- Cisco has released free software updates that address the vulnerability described in this advisory. Customers with service contracts that entitle them to regular software updates should obtain security fixes through their usual update channels.
- 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:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.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.
- The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool.
- When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories 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 TAC: https://www.cisco.com/c/en/us/support/web/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
The fix for this vulnerability is distributed through an updated version of the Content Scanner Tools package. Content Scanner Tools versions 23.3.0.4823 and later contain the fix for this vulnerability.
The updated version of Content Scanner Tools is included by default in Cisco AsyncOS for Cisco Secure Email Software releases 15.5.1-055 and later.
Update the Content Scanner Tools
Updating the Content Scanner Tools does not require a software upgrade or a product restart. Customers who configured an automated Content Scanner Tools update may not be required to perform any action to address this vulnerability.
Manual Update
To manually update the Content Scanner Tools, use the command CLI contentscannerupdate, as shown in the following example:
cisco-esa> contentscannerupdate
Requesting check for new Content Scanner updates.
For instructions on how to verify the current version, see the Vulnerable Products section of this advisory.
Automatic Update
To enable automatic updates, complete the following steps on the web management interface:
- Choose Security Services > Service Updates.
- Click Edit Update Settings.
- Click the Automatic Updates check box.
- Click Submit.
- Choose Commit Changes on the top right of the page.
- Confirm the uncommitted changes by clicking on Commit Changes.
For customers who use Cisco Secure Email Cloud Gateway, no action is required. Cisco has taken actions to protect the infrastructure from this vulnerability, and a fixed version of Content Scanner Tools will be deployed as part of the standard upgrade processes for the environment.
The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
Exploitation and Public Announcements
- The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
Source
- This vulnerability was found during the resolution of a Cisco TAC support case.
URL
Source: