Cisco Security Advisory
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CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:N/E:X/RL:X/RC:X
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On January 18, 2023, Cisco disclosed the following:
A vulnerability in the URL filtering mechanism of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the URL reputation filters on an affected device.
This vulnerability is due to improper processing of URLs. An attacker could exploit this vulnerability by crafting a URL in a particular way. A successful exploit could allow the attacker to bypass the URL reputation filters that are configured for an affected device, which could allow malicious URLs to pass through the device.After additional investigation, it was determined that this vulnerability is not exploitable. For more information, see the Workarounds section of this advisory.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-url-bypass-WbMQqNJh
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Vulnerable Products
At the time of publication, this vulnerability affected all releases of Cisco AsyncOS Software for Cisco ESA that did not have the Anti-Spam feature enabled.
See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability.
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Administrators should follow the Best Practice Guide for Anti-Spam, Anti-Virus, Graymail and Outbreak Filters and should ensure that the Cisco Anti-Spam feature is enabled because it contains rules designed to identify specially crafted URLs. It is also recommended that all positive verdicts be either dropped or quarantined.
While this workaround has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.
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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.
Fixed Releases
For information about fixed software releases, see the Details section in the bug ID(s) at the top of this advisory.
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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.
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Cisco would like to thank Roy Barkay Yosef and Chen Farchi for reporting this vulnerability.
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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.
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Show LessVersion Description Section Status Date 1.1 Updated the advisory SIR to Informational. Updated the Summary to indicate that the issue is not exploitable. Updated information about vulnerable products. Updated the Workarounds section. Header, Summary, Affected Products, Workarounds Final 2023-FEB-13 1.0 Initial public release. — Final 2023-JAN-18
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