^{CVE-2023-32250:}Linux kernel ksmbd vulnerability allows code execution through SMB2_SESSION_SETUP command race condition

Overview

The vulnerability (CVE-2023-32250) affects the ksmbd module in the Linux kernel, which is a high-performance in-kernel SMB server. The flaw specifically exists in how the kernel handles SMB2_SESSION_SETUP commands. Due to insufficient locking mechanisms, concurrent operations on shared objects can lead to race conditions. An attacker who can connect to the SMB service could exploit this vulnerability to trigger a race condition, potentially resulting in memory corruption and arbitrary code execution with kernel privileges. Since the code executes in kernel context, successful exploitation could lead to complete system compromise, allowing attackers to bypass security controls, access sensitive information, or take full control of the affected system.

Remediation

1. Update the Linux kernel to a version that contains the patch for CVE-2023-32250.
2. If immediate patching is not possible, consider disabling the ksmbd module if it's not essential for operations:
   • Run modprobe -r ksmbd to unload the module
   • Prevent it from loading at boot by adding ksmbd to a blacklist file in /etc/modprobe.d/
3. If ksmbd must be used, restrict access to the SMB service using firewall rules to limit exposure to trusted networks only.
4. Monitor system logs for suspicious SMB-related activities that might indicate exploitation attempts.
5. Follow vendor-specific guidance from your Linux distribution for additional security measures and patch availability.

References

1. Red Hat Security Advisory: https://access.redhat.com/security/cve/CVE-2023-32250
2. Red Hat Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2208849
3. NetApp Security Advisory: https://security.netapp.com/advisory/ntap-20230824-0004/
4. Zero Day Initiative Advisory: https://www.zerodayinitiative.com/advisories/ZDI-23-698/
5. Common Weakness Enumeration: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)