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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2019.2446 Cisco Web Security Appliance Denial of Service Vulnerabilities 4 July 2019 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Cisco Web Security Appliance Publisher: Cisco Systems Operating System: Network Appliance Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2019-1886 CVE-2019-1884 Original Bulletin: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190703-wsa-dos https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190703-asyncos-wsa Comment: This bulletin contains two (2) Cisco Systems security advisories. - --------------------------BEGIN INCLUDED TEXT-------------------- Cisco Web Security Appliance HTTPS Certificate Denial of Service Vulnerability Priority: High Advisory ID: cisco-sa-20190703-wsa-dos First Published: 2019 July 3 16:00 GMT Version 1.0: Final Workarounds: No workarounds available Cisco Bug IDs: CSCvo33747 CVE-2019-1886 CWE-20 CVSS Score: 8.6 AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X Summary o A vulnerability in the HTTPS decryption feature of Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to insufficient validation of Secure Sockets Layer (SSL) server certificates. An attacker could exploit this vulnerability by installing a malformed certificate in a web server and sending a request to it through the Cisco WSA. A successful exploit could allow the attacker to cause an unexpected restart of the proxy process on an affected device. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/ cisco-sa-20190703-wsa-dos Affected Products o Vulnerable Products This vulnerability affects Cisco AsyncOS Software for Cisco WSA, both virtual and hardware appliances, when the devices have the HTTPS Proxy feature enabled and have at least one decryption policy configured. The HTTPS Proxy feature is disabled by default. For information about which Cisco AsyncOS Software releases are vulnerable, see the Fixed Software section of this advisory. To determine whether the HTTPS Proxy feature is enabled for a WSA, administrators can log in to the web interface of the WSA and navigate to Security Services > HTTPS Proxy . The value in the HTTPS Proxy field indicates whether the feature is enabled or disabled. Products Confirmed Not Vulnerable Only products listed in the Vulnerable Products section of this advisory are known to be affected by this vulnerability. Indicators of Compromise o Exploitation of this vulnerability will cause the proxy process to generate a core file with a particular backtrace. Contact the Cisco Technical Assistance Center (TAC) to review the core file and determine whether the device has been compromised by exploitation of this vulnerability and to identify the IP address of the server that is hosting the malformed certificate. Workarounds o There are no workarounds that address this vulnerability. It is possible to mitigate the impact of this vulnerability by bypassing decryption for web servers that are hosting malformed certificates that exploit this vulnerability. For details about how to configure the bypass, refer to AsyncOS User Guide . Fixed Software o Cisco has released free software updates that address the vulnerability described in this advisory. 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. When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts 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 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 Customers are advised to upgrade to an appropriate fixed software release as indicated in the following table: Cisco AsyncOS Software Major Release First Fixed Release Prior to 10.5 Migrate to 10.5.5-005 10.5 10.5.5-005 11.5 11.5.2-020 11.7 Not vulnerable In most cases, the software can be upgraded over the network by using the System Upgrade options in the Cisco WSA web interface. To upgrade a device by using the web interface: 1. Choose System Administration > System Upgrade . 2. Click Upgrade Options . 3. Choose Download and Install . 4. Choose the release to upgrade to. 5. In the Upgrade Preparation area, choose the appropriate options. 6. Click Proceed to begin the upgrade. A progress bar displays the status of the upgrade. After the upgrade is complete, the device reboots. 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 This vulnerability was found during the resolution of a Cisco TAC support case. 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. URL o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/ cisco-sa-20190703-wsa-dos Revision History o +---------+---------------------------+---------+--------+---------------+ | Version | Description | Section | Status | Date | +---------+---------------------------+---------+--------+---------------+ | 1.0 | Initial public release. | - | Final | 2019-July-03 | +---------+---------------------------+---------+--------+---------------+ - -------------------------------------------------------------------------------- Cisco Web Security Appliance Web Proxy Denial of Service Vulnerability Priority: High Advisory ID: cisco-sa-20190703-asyncos-wsa First Published: 2019 July 3 16:00 GMT Version 1.0: Final Workarounds: No workarounds availableCisco Bug IDs: CSCvo29853 CVE-2019-1884 CWE-20 CVSS Score: 7.7 AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X Summary o A vulnerability in the web proxy functionality of Cisco AsyncOS Software for Cisco Web Security Appliance (WSA) could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to insufficient input validation mechanisms for certain fields in HTTP/HTTPS requests sent through an affected device. A successful attacker could exploit this vulnerability by sending a malicious HTTP/HTTPS request through an affected device. An exploit could allow the attacker to force the device to stop processing traffic, resulting in a DoS condition. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is available at the following link: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/ cisco-sa-20190703-asyncos-wsa Affected Products o Vulnerable Products This vulnerability affects Cisco AsyncOS Software for Cisco Web Security Appliance, both virtual and hardware appliances. For information about which Cisco AsyncOS Software releases are vulnerable, see the Fixed Software section of this advisory. 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: Email Security Appliance (ESA), both virtual and hardware appliances Security Management Appliance (SMA), both virtual and hardware appliances Indicators of Compromise o Exploitation of this vulnerability could cause the Cisco WSA to generate a core file for the main proxy process. Contact the Cisco Technical Assistance Center (TAC) to review the core file and determine whether the device has been compromised by exploitation of this vulnerability. Workarounds o There are no workarounds that address this vulnerability. Fixed Software o Cisco has released free software updates that address the vulnerability described in this advisory. 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. When considering software upgrades, customers are advised to regularly consult the advisories for Cisco products, which are available from the Cisco Security Advisories and Alerts 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 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 Customers are advised to upgrade to an appropriate fixed software release as indicated in the following table: Cisco AsyncOS Software Major Release First Fixed Release 10.1 10.5.5-005 10.5 10.5.5-005 11.5 11.5.2-020 11.7 11.7.0-407 In most cases, the software can be upgraded over the network by using the System Upgrade options in the Cisco WSA web interface. To upgrade a device by using the web interface: 1. Choose System Administration > System Upgrade . 2. Click Upgrade Options . 3. Choose Download and Install . 4. Choose the release to upgrade to. 5. In the Upgrade Preparation area, choose the appropriate options. 6. Click Proceed to begin the upgrade. A progress bar displays the status of the upgrade. After the upgrade is complete, the device reboots. 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 This vulnerability was found during the resolution of a Cisco TAC support case. 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. URL o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/ cisco-sa-20190703-asyncos-wsa Revision History o +---------+---------------------------+---------+--------+---------------+ | Version | Description | Section | Status | Date | +---------+---------------------------+---------+--------+---------------+ | 1.0 | Initial public release. | - | Final | 2019-July-03 | +---------+---------------------------+---------+--------+---------------+ - --------------------------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 auscert@auscert.org.au and we will forward your request to the appropriate person. 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If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: https://www.auscert.org.au/bulletins/ =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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