-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Advisory ID: SYSS-2015-003 Product: Kaspersky Small Office Security (KSOS) Vendor: Kaspersky Lab ZAO Affected Version(s): 13.0.4.233 Tested Version(s): 13.0.4.233 Vulnerability Type: Authentication Bypass Using an Alternate Path or Channel (CWE-288) Risk Level: Medium Solution Status: Fixed Vendor Notification: 2015-02-19 Solution Date: 2015-10-01 Public Disclosure: 2015-10-01 CVE Reference: Not yet assigned Authors of Advisory: Matthias Deeg and Sven Freund (SySS GmbH) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overview: Kaspersky Small Office Security is an endpoint protection software with many features like malware protection, defences against phishing attacks and exploits, data encryption and data backup functionality. The vendor Kaspersky describes the product as follows (see [1]): "Kaspersky Small Office Security delivers business-grade protection technologies that are designed to be simple to install, configure and run. The solution protects your Windows-based PCs & file servers and Android smartphones and tablets to safeguard your online banking transactions, your business data and the information your customers entrust to you." ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vulnerability Details: The Kaspersky Small Office Security software allows users to disable the offered protection by entering a so-called unload password. Beside the graphical user interface (GUI) authentication, it is also possible to manually deactivate the protection over the command-line interface using the Kaspersky software tool avp.exe. By analyzing the password-based authentication for unloading the Kaspersky Small Office Security protection, the SySS GmbH found out, that the password comparison is done within the process avp.exe (actually within the module avpmain.dll), which runs or can be run in the context of the current Windows user, who can also be a standard, limited user. This fact allows a further analysis and the manipulation of the password comparison during runtime without administrative privileges, as every user is able to debug and manipulate the processes running with her user privileges. In order to bypass the password-based authentication to deactivate the protection of Kaspersky Small Office Security in an unauthorized manner, an attacker only has to patch this password comparison, so that it always returns true, for example by comparing the correct unload password with itself or by modifying the program control flow. The SySS GmbH also found out, that by modifying the software tool avp.exe, the Kaspersky Small Office Security can also be deactivated completely even when no password was set for protecting administrative functions. The intended behavior of the software tool avp.exe in this case is to deny access to the requested function, for example "exit", due to a disabled password protection. Thus, a limited Windows user or malware running in the context of such a user is able to unload Kaspersky Small Office Security in an unauthorized manner regardless of the configured password protection. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Proof of Concept (PoC): The SySS GmbH developed a proof-of-concept software tool named UnloadKSOS for deactivating Kaspersky Small Office Security in an unauthorized manner. The following output exemplarily shows a successful deactivation of Kaspersky Small Office Security: >UnloadKSOS.exe ____________________________________________________________ / _____ _____ _____ \ / / ___| / ___/ ___| \ | \ `--. _ _\ `--.\ `--. | | `--. \ | | |`--. \`--. \ | | /\__/ / |_| /\__/ /\__/ / | \ \____/ \__, \____/\____/ ... unloads KSOS! / \ __/ | / / |___/ _________________________________________/ / _________________/ (__) /_/ (oo) /------\/ / |____|| * || || ^^ ^^ SySS Unload KSOS v1.0 by Matthias Deeg & Sven Freund - SySS GmbH (c) 2015 [+] Found location of the executable file avp.exe [+] Created new instance of the Kaspersky Small Office Security process avp.exe [+] The Kaspersky Small Office Security process was patched successfully. Kaspersky Small Office Security will now exit without a password. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Solution: According to information by Kaspersky, the described security issue has been fixed in newer software releases. Please contact the manufacturer for further information or support. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclosure Timeline: 2015-02-19: Vulnerability reported to manufacturer 2015-02-19: Manufacturer acknowledges e-mail with SySS security advisory 2015-03-17: Rescheduling of the publication date in agreement with the manufacturer 2015-04-14: Rescheduling of the publication date in agreement with the manufacturer 2015-09-28: SySS asks for further information about software fix 2015-10-01: Public release of security advisory on agreed publication date ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ References: [1] Product Web site for Kaspersky Small Office Security http://www.kaspersky.com/small-office-security [2] SySS Security Advisory SYSS-2015-003 https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2015-003.txt [3] SySS Responsible Disclosure Policy https://www.syss.de/en/news/responsible-disclosure-policy/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Credits: This security vulnerability was found by Matthias Deeg and Sven Freund of the SySS GmbH. E-Mail: matthias.deeg (at) syss.de Public Key: https://www.syss.de/fileadmin/dokumente/Materialien/PGPKeys/Matthias_Deeg.asc Key fingerprint = D1F0 A035 F06C E675 CDB9 0514 D9A4 BF6A 34AD 4DAB E-Mail: sven.freund (at) syss.de Public Key: https://www.syss.de/fileadmin/dokumente/Materialien/PGPKeys/Sven_Freund.asc Key fingerprint = DCDB 7627 C1E3 9CE8 62DF 2666 8A5F A853 415D 46DC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclaimer: The information provided in this security advisory is provided "as is" and without warranty of any kind. Details of this security advisory may be updated in order to provide as accurate information as possible. The latest version of this security advisory is available on the SySS Web site. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Copyright: Creative Commons - Attribution (by) - Version 3.0 URL: http://creativecommons.org/licenses/by/3.0/deed.en -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCgAGBQJWDPBnAAoJENmkv2o0rU2rVywQAIzyHG0UmuI4yMQwj5J3DEFG hD8yWjUjkLJu6+ym8c9Iu9qxB9Q07wbDl+rUzjzWZ8ZPpwdfh3fJ00gQjLYlmeKe sn+Smi1gWeDmLa3PjS0Zxv74OeFl+DyDjcxeHKfprNoKlyVAMm2VOQBn9m3UigVD llMTP+MKLT5SNlE9ZO7r7MBC09b/oP5k2XWkJnZxqbmo+lZNSNoG4x1rHvLzVs7I jNAymcGm6TZVxL7hQ0LRGAjIXQSziNsrY2TmnHaUZi+t32Q24m05nnmJQtAOitUs MdegKlumEiU1BHMHCjpAis+R7bmhg9VNVsD17kyvignQt5zFPIKmQQrUplMzBItB X/IPVejVWF1k8l/TQGrED5apxEXO5N+ZIo2UdmS5HupOpWQ9WX95QDxpChlUZe6K 19oY257gufCubnzWx8QFj1SNl1BXyB4Icq+E21OkUVnZYE8qufdldN0hUOMc7PEl PCSakThGbT4BTjEztFD3UbblqMmPBEVI4lBcWBCHqHJJnSKTQF0FSGTEgWrRZLO8 fa/GtaZCg2ceMP/PF8ooDmftzrin5sSQTV7A0lrWNMzlQdMJERP5qDrfpXNERxmw eGoUwRmSMEZpN9SbIHUFK6GH3QG1zi0tCN5UjGaIFjgKoV4QdDP0V0mJ6AzEewgH XnYrKxMmPS1yBTic3UNQ =tA90 -----END PGP SIGNATURE-----