CVE-2017-18241:NULL Pointer Dereference in Linux Kernel's F2FS File System

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CVE-2017-18241 is a vulnerability in the Linux kernel's Flash-Friendly File System (F2FS) implementation. The issue exists in the fs/f2fs/segment.c file in Linux kernel versions before 4.13. When users utilize the noflush_merge option, it can trigger a NULL value for a flush_cmd_control data structure. This NULL pointer dereference leads to a kernel panic, resulting in denial of service (DoS) conditions. The vulnerability is classified as CWE-476 (NULL Pointer Dereference).

Overview

This vulnerability affects the F2FS file system implementation in the Linux kernel. F2FS (Flash-Friendly File System) is designed for NAND flash memory-based storage devices. The issue occurs when the noflush_merge option is used, causing the system to attempt to access a NULL flush_cmd_control structure. This leads to a kernel panic and system crash, effectively creating a denial of service condition. Local users with sufficient privileges to mount or configure F2FS file systems can exploit this vulnerability to disrupt system operations. The vulnerability is particularly concerning in multi-user environments where local users could intentionally trigger system crashes.

Remediation

To address this vulnerability, system administrators should:

  1. Update the Linux kernel to version 4.13 or later, which contains the fix for this issue.
  2. Apply the specific patch referenced in the commit d4fdf8ba0e5808ba9ad6b44337783bd9935e0982 if updating the entire kernel is not immediately possible.
  3. For Ubuntu users, apply the security updates referenced in USN-3910-1 and USN-3910-2.
  4. For Debian users, apply the security updates referenced in DSA-4187 and DSA-4188.
  5. If updates cannot be applied immediately, consider disabling the use of F2FS file systems or restricting the ability to mount F2FS file systems with custom options to trusted users only.
  6. Monitor system logs for potential exploitation attempts, which would typically appear as unexpected kernel panics related to F2FS operations.

References

  1. Linux Kernel Patch: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d4fdf8ba0e5808ba9ad6b44337783bd9935e0982
  2. GitHub Mirror of Linux Kernel Patch: https://github.com/torvalds/linux/commit/d4fdf8ba0e5808ba9ad6b44337783bd9935e0982
  3. Ubuntu Security Notice USN-3910-1: https://usn.ubuntu.com/3910-1/
  4. Ubuntu Security Notice USN-3910-2: https://usn.ubuntu.com/3910-2/
  5. Debian Security Advisory DSA-4187: https://www.debian.org/security/2018/dsa-4187
  6. Debian Security Advisory DSA-4188: https://www.debian.org/security/2018/dsa-4188
  7. Common Weakness Enumeration: CWE-476 (NULL Pointer Dereference)

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