CVE-2023-52752

What it actually does

Use-after-free when cifs_debug_data_proc_show() accesses SMB session structures that are being torn down (SES_EXITING status) during concurrent mount/umount operations while reading /proc/fs/cifs/DebugData.

Why it matters to the business

Local users on Linux systems with the SMB client can trigger kernel crashes or potential code execution, leading to denial of service, data corruption, or privilege escalation on servers and workstations that mount SMB shares.

How an attack unfolds

An attacker with local access repeatedly mounts and unmounts SMB sessions while simultaneously reading the CIFS DebugData proc file, causing the kernel to dereference freed session objects and resulting in a general protection fault that may be leveraged for further exploitation.

How to fix it

Update the Linux kernel to a version containing commit 2abdf136784b7edaec7ffe0f4b461b63f9c4c4de or later; rebuild and reboot with the patched kernel. Disable or restrict access to /proc/fs/cifs/DebugData as a temporary mitigation if patching is delayed.

How to confirm the fix worked

Verify the running kernel contains commit 2abdf136784b7edaec7ffe0f4b461b63f9c4c4de via git log or uname; attempt to read /proc/fs/cifs/DebugData during active mount/umount cycles and confirm absence of general protection faults referencing cifs_debug_data_proc_show.

Typical attack path

1. Obtain local user access on a Linux system using the CIFS/SMB client
2. Trigger repeated mount and unmount operations on SMB shares
3. Read /proc/fs/cifs/DebugData concurrently to hit the use-after-free
4. Exploit the resulting kernel memory corruption for code execution or crash

How to detect it

Search kernel logs for general protection faults with call traces containing cifs_debug_data_proc_show, cifs_debug_tcon, and SES_EXITING references; correlate with processes reading /proc/fs/cifs/DebugData during mount/umount activity.

• cifs_debug_data_proc_show
• cifs_debug_tcon
• SES_EXITING
• general protection fault.*cifs
• /proc/fs/cifs/DebugData

What your security team should do

• Apply the fixed kernel commit immediately on all systems exposing SMB client functionality
• Monitor for kernel oops involving cifs_debug_tcon and cifs_debug_data_proc_show
• Restrict local user access to procfs CIFS debug files until patched
• Test patched kernels in staging before broad deployment due to filesystem driver changes