14 February 2023
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2023.0274.2 Cisco Email Security Appliance URL Filtering Bypass Vulnerability 14 February 2023 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco Email Security Appliance (ESA) Publisher: Cisco Systems Operating System: Cisco Resolution: Patch/Upgrade CVE Names: CVE-2023-20057 Original Bulletin: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-url-bypass-WbMQqNJh Comment: CVSS (Max): 4.7 CVE-2023-20057 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N) CVSS Source: Cisco Systems Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N Revision History: February 14 2023: Updated the advisory SIR to informational and summary to indicate the issue is not exploitable. Also updated information about vulnerable products and workarounds. January 19 2023: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- Cisco Email Security Appliance URL Filtering Bypass Vulnerability Priority: Informational Advisory ID: cisco-sa-esa-url-bypass-WbMQqNJh First Published: 2023 January 18 16:00 GMT Last Updated: 2023 February 13 15:30 GMT Version 1.1: Final Workarounds: Yes Cisco Bug IDs: CSCwb58117 CVE Names: CVE-2023-20057 Summary o 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 Affected Products o 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. Workarounds o 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. Fixed Software o 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. Exploitation and Public Announcements o 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. Source o Cisco would like to thank Roy Barkay Yosef and Chen Farchi for reporting this vulnerability. Cisco Security Vulnerability Policy o 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. Subscribe to Cisco Security Notifications o Subscribe Related to This Advisory o URL o https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-url-bypass-WbMQqNJh Revision History o +---------+--------------------------+-------------+--------+-------------+ | Version | Description | Section | Status | Date | +---------+--------------------------+-------------+--------+-------------+ | | Updated the advisory SIR | | | | | | to Informational. | | | | | | Updated the Summary to | Header, | | | | | indicate that the issue | Summary, | | | | 1.1 | is not exploitable. | Affected | Final | 2023-FEB-13 | | | Updated information | Products, | | | | | about vulnerable | Workarounds | | | | | products. Updated the | | | | | | Workarounds section. | | | | +---------+--------------------------+-------------+--------+-------------+ | 1.0 | Initial public release. | - | Final | 2023-JAN-18 | +---------+--------------------------+-------------+--------+-------------+ Legal Disclaimer o THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME. A standalone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy and may lack important information or contain factual errors. The information in this document is intended for end users of Cisco products. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to firstname.lastname@example.org and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. 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