CVE-2021-27216:Exim 4 before 4.94.2 contains a race condition vulnerability that allows local users to delete arbitrary files with root privileges.

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Description Preview

Exim 4 versions prior to 4.94.2 contain a race condition vulnerability (CWE-362) in the delete_pid_file functionality. Local attackers can exploit this vulnerability by leveraging the race condition using the -oP and -oPX command-line options. This allows unprivileged users to delete arbitrary files on the system with root privileges due to unnecessary privilege execution during certain operations.

Overview

This vulnerability affects Exim 4 mail transfer agent versions prior to 4.94.2. The issue stems from a race condition in the delete_pid_file functionality that occurs when the mail server handles PID files. By manipulating the -oP and -oPX command-line options, a local attacker can cause Exim to delete arbitrary files on the system with root privileges. This vulnerability is particularly dangerous as it allows privilege escalation through file deletion capabilities, potentially leading to system compromise or denial of service conditions.

Remediation

To mitigate this vulnerability, system administrators should:

  1. Update Exim to version 4.94.2 or later as soon as possible.
  2. If immediate updating is not possible, consider restricting local access to the Exim binary or implementing additional access controls.
  3. Monitor system logs for suspicious Exim command executions, particularly those using the -oP or -oPX options.
  4. Apply principle of least privilege to the Exim service where possible to minimize potential impact.
  5. Consider implementing file integrity monitoring to detect unauthorized file deletions.

References

  1. Exim Security Advisory: https://www.exim.org/static/doc/security/CVE-2020-qualys/CVE-2020-28007-LFDIR.txt
  2. CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
  3. MITRE CVE-2021-27216: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-27216

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

Focus on What Matters

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

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