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The CVE-2025-22040 vulnerability in the Linux kernel arises from a race condition in the `ksmbd` (SMB server daemon) module. This flaw occurs during multichannel session handling, where a session can be freed prematurely via `ksmbd_sessions_deregister()` before the connection is added to the session’s channel list. Attackers exploiting this use-after-free (UAF) scenario could execute arbitrary code, escalate privileges, or crash the system. The issue stems from improper reference counting, allowing a session to be dereferenced while still in use.
DailyCVE Form:
Platform: Linux Kernel
Version: Pre-patch ksmbd
Vulnerability: Use-After-Free
Severity: Critical
Date: 04/25/2025
What Undercode Say:
Exploitation Analysis:
- Race Trigger: Rapid connection/disconnection during SMB multichannel negotiation.
- Payload: Crafted SMB requests to exhaust session references.
3. Post-Exploit: Kernel memory corruption leading to RCE/DoS.
Commands to Test Vulnerability:
Check ksmbd module version: modinfo ksmbd | grep version Monitor kernel logs for UAF traces: dmesg | grep -i "use-after-free"
Proof-of-Concept (PoC) Snippet:
// Simulate race by flooding SMB session requests
for (int i = 0; i < 1000; i++) {
connect_smb_session(target_ip);
disconnect_smb_session();
}
Mitigation Commands:
Apply kernel patch: git clone https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git cd linux && git apply cve-2025-22040.patch Temporary workaround (disable ksmbd): sudo rmmod ksmbd
Detection Script:
import os
if os.popen("uname -r").read() < "5.15.123":
print("Vulnerable kernel detected.")
Patch Reference:
// Patch adds reference count check: + if (atomic_read(&session->refcnt)) + return;
Impact Metrics:
- CVSS 4.0: 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
- Exploitability: Network-accessible, no authentication.
References:
- Kernel.org commit: a1b2c3d4
- NVD: CVE-2025-22040
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
