CVE-2023-53794: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53794 is a use-after-free vulnerability in the Linux kernel's CIFS (Common Internet File System) subsystem, specifically within the SMB2 reconnect logic. The flaw occurs in smb2_reconnect_server(), where an exiting session can be collected and accessed after it has begun its teardown process, leading to a use-after-free condition. Affected Linux kernel versions span from the initial commit (1da177e4c3f4) up to the patched releases: 6.1.47, 6.4.12, and 6.5. The vulnerability was published on December 9, 2025, and carries an estimated CVSS severity of Medium (Feedly, EUVD).

The root cause is a use-after-free (CWE-416) in the Linux kernel's CIFS driver. During SMB2 server reconnection, smb2_reconnect_server() iterates over server->smb_ses_list and may collect a session that is in the process of exiting. The exiting session remains in the list until it completes cifs_free_ipc() and logoff() before removing itself, creating a window where a dangling pointer to the freed session object can be dereferenced. The fix prevents collection of sessions in the exiting state during reconnect enumeration (Feedly, Kernel Git).

Exploitation of this vulnerability could result in kernel memory corruption due to the use-after-free condition, potentially leading to a system crash (denial of service) or, in more severe scenarios, privilege escalation or arbitrary code execution in kernel context. The impact is confined to systems using the CIFS/SMB2 client functionality in the Linux kernel, particularly those that experience SMB server reconnection events. Confidentiality, integrity, and availability of the affected system may all be at risk depending on how the freed memory is subsequently reused (Feedly).

No public proof-of-concept exploit code or in-the-wild exploitation has been reported for CVE-2023-53794. The EPSS score is approximately 0.017% (0.000170), indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Detection plugins are available from Qualys (IDs: 761056, 761719) and Nessus (multiple plugin IDs), indicating scanner-level coverage for affected systems (Feedly).

The Linux kernel has been patched in stable releases 6.1.47, 6.4.12, and 6.5. The fix modifies smb2_reconnect_server() to skip sessions that are in an exiting state, preventing the use-after-free condition. Users should update their Linux kernel to one of the patched versions. Downstream distributions such as SUSE have also released updated kernel packages incorporating this fix (Kernel Git, Linux Security SUSE). As a temporary workaround where patching is not immediately possible, disabling CIFS/SMB2 mounts can eliminate exposure to this code path.

Coverage of CVE-2023-53794 has been limited to security scanner vendors (Tenable/Nessus, Qualys) and Linux distribution security advisories, particularly from SUSE and openSUSE. No notable independent researcher commentary or significant social media discussion has been identified for this vulnerability (Linux Security SUSE, openSUSE).