CVE-2021-30120:Kaseya VSA before 9.5.7 contains a two-factor authentication (2FA) bypass vulnerability due to client-side enforcement rather than server-side validation.

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CVE-2021-30120 affects Kaseya VSA versions prior to 9.5.7. The vulnerability allows attackers to bypass two-factor authentication (2FA) by manipulating client-side parameters. During the login process, after a user authenticates with username and password, the server sends a response to the client containing boolean values "MFARequired" and "MFAEnroled". An attacker with valid credentials can use an intercepting proxy (such as Burp Suite) to modify the "MFARequired" value from True to False. This manipulation allows the attacker to bypass the 2FA requirement completely, as the authentication mechanism is enforced client-side rather than server-side, effectively rendering the 2FA protection useless.

Overview

This vulnerability (CWE-669: Incorrect Resource Transfer Between Spheres) in Kaseya VSA represents a critical security flaw in the authentication mechanism. Two-factor authentication is designed to provide an additional layer of security beyond passwords, but this implementation flaw undermines that protection entirely. The vulnerability was discovered during the investigation of the widespread Kaseya supply chain ransomware attack in July 2021. The Dutch Institute for Vulnerability Disclosure (DIVD) had previously identified and reported this vulnerability to Kaseya before the attack occurred. This vulnerability could allow an attacker with valid credentials to gain unauthorized access to Kaseya VSA systems without needing to provide the second authentication factor, potentially leading to complete system compromise.

Remediation

Organizations using Kaseya VSA should immediately:

  1. Upgrade to Kaseya VSA version 9.5.7 or later, which properly implements server-side 2FA validation.
  2. Review authentication logs for any suspicious login activities that might indicate exploitation attempts.
  3. Enforce strong password policies for all user accounts.
  4. Consider implementing additional network-level controls to restrict access to the Kaseya VSA interface.
  5. Monitor for unusual activities that could indicate unauthorized access.
  6. If unable to update immediately, consider implementing additional network security measures such as IP restrictions or VPN requirements for accessing the Kaseya VSA interface.

References

  1. DIVD Limited Disclosure Report: https://csirt.divd.nl/2021/07/07/Kaseya-Limited-Disclosure/
  2. DIVD CVE-2021-30120 Details: https://csrit.divd.nl/CVE-2021-30120
  3. DIVD Case DIVD-2021-00011: https://csrit.divd.nl/DIVD-2021-00011
  4. CWE-669: Incorrect Resource Transfer Between Spheres: https://cwe.mitre.org/data/definitions/669.html

Industry ExposureMost to least
This section illustrates the prevalence of a specific Common Vulnerabilities and Exposures (CVE) across various industries based on customer reports. The ranking displays industries from the most to least affected by this particular vulnerability, offering valuable insight into where this CVE has been most frequently observed. This information can help organizations within these sectors prioritize their security efforts, understand their relative risk exposure compared to their peers, and focus remediation strategies where they are most needed. By understanding the industry-specific impact, organizations can make more informed decisions regarding patching, resource allocation, and overall risk management related to this CVE.

  1. Accommodation & Food Services
    Accommodation & Food Services
  2. Administrative, Support, Waste Management & Remediation Services
    Administrative, Support, Waste Management & Remediation Services
  3. Agriculture, Forestry Fishing & Hunting
    Agriculture, Forestry Fishing & Hunting
  4. Arts, Entertainment & Recreation
    Arts, Entertainment & Recreation
  5. Construction
    Construction
  6. Educational Services
    Educational Services
  7. Finance and Insurance
    Finance and Insurance
  8. Health Care & Social Assistance
    Health Care & Social Assistance
  9. Information
    Information
  10. Management of Companies & Enterprises
    Management of Companies & Enterprises
  11. Manufacturing
    Manufacturing
  12. Mining
    Mining
  13. Other Services (except Public Administration)
    Other Services (except Public Administration)
  14. Professional, Scientific, & Technical Services
    Professional, Scientific, & Technical Services
  15. Public Administration
    Public Administration
  16. Real Estate Rental & Leasing
    Real Estate Rental & Leasing
  17. Retail Trade
    Retail Trade
  18. Transportation & Warehousing
    Transportation & Warehousing
  19. Utilities
    Utilities
  20. Wholesale Trade
    Wholesale Trade

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