CVE-2021-44142:Out-of-bounds heap read and write vulnerability in Samba's vfs_fruit module allows remote code execution as root.

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A critical vulnerability (CVE-2021-44142) affects Samba's vfs_fruit module, which provides compatibility with Apple SMB clients. In versions prior to 4.13.17, 4.14.12, and 4.15.5, the module improperly handles extended file attributes (xattr), allowing attackers to perform out-of-bounds heap read and write operations. An attacker with write access to extended file attributes can craft malicious xattr data to execute arbitrary code with the privileges of the smbd process, which typically runs as root. This vulnerability was demonstrated at the Pwn2Own Austin competition.

Overview

CVE-2021-44142 is a serious security flaw in Samba's vfs_fruit module that affects all Samba installations with this module enabled. The vulnerability stems from improper handling of extended file attributes (EA/xattr) which are used by the module to enhance compatibility with Apple SMB clients and Netatalk 3 AFP fileservers. The issue combines both CWE-125 (Out-of-bounds Read) and CWE-787 (Out-of-bounds Write) vulnerabilities, allowing attackers to read from and write to memory locations outside the intended boundaries. This can lead to information disclosure, memory corruption, and ultimately arbitrary code execution with root privileges. The vulnerability is particularly dangerous as it can be exploited remotely by any user who has permission to modify extended attributes on files in the Samba share.

Remediation

To remediate this vulnerability, system administrators should:

  1. Update Samba to a patched version:

    • Version 4.13.17 or later
    • Version 4.14.12 or later
    • Version 4.15.5 or later

  2. If immediate updating is not possible, consider one of these mitigations:

    • Disable the vfs_fruit module in your Samba configuration
    • Restrict write access to the Samba share to trusted users only
    • Use network segmentation to limit access to the Samba server

  3. After updating, restart the Samba service to ensure the patch takes effect.

  4. Review system logs for any signs of exploitation attempts.

  5. Consider implementing additional security controls such as file integrity monitoring to detect unauthorized changes to system files.

References

  1. Samba Security Advisory: https://www.samba.org/samba/security/CVE-2021-44142.html
  2. Zero Day Initiative analysis: https://www.zerodayinitiative.com/blog/2022/2/1/cve-2021-44142-details-on-a-samba-code-execution-bug-demonstrated-at-pwn2own-austin
  3. Samba Bug Report: https://bugzilla.samba.org/show_bug.cgi?id=14914
  4. CERT Vulnerability Note: https://kb.cert.org/vuls/id/119678
  5. Gentoo Linux Security Advisory: https://security.gentoo.org/glsa/202309-06

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

Focus on What Matters

  1. See Everything.
  2. Identify True Risk.
  3. Proactively Mitigate Threats.

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