CVE-2022-50856

What it actually does

Failure to release an allocated xid before returning from cifs_ses_add_channel results in a resource leak within the CIFS kernel module.

Why it matters to the business

Repeated channel additions on CIFS mounts can gradually exhaust kernel resources, leading to degraded performance or instability in file-sharing operations over extended periods; the large number of downstream dependents increases the scope of exposure across Linux environments.

How an attack unfolds

An attacker with the ability to trigger repeated CIFS session channel additions can cause progressive resource exhaustion; no named threat actors are associated with active exploitation of this issue.

How to fix it

Upgrade affected Linux kernel packages to a version containing commit 7286f875510486fdc2fc426b7c826262e2283a65 or later; for rdesktop on Debian 11-14 apply version 1.8.4-1 or newer. Prioritize patching systems with high CIFS usage given the published remediation timeline.

How to confirm the fix worked

Confirm the presence of commit 7286f875510486fdc2fc426b7c826262e2283a65 in the running kernel source or verify package versions match the listed fixed releases; review kernel logs for xid allocation patterns before and after the update.

Typical attack path

1. Establish a CIFS connection requiring multi-channel session setup
2. Invoke cifs_ses_add_channel repeatedly through legitimate or crafted mount operations
3. Observe gradual depletion of xid resources without explicit error until system impact occurs

How to detect it

Review kernel logs and audit trails for repeated cifs_ses_add_channel calls without corresponding xid releases; correlate with CIFS mount activity in system call traces or performance counters showing resource growth.

What your security team should do

• Apply kernel and rdesktop updates to the specified fixed versions immediately on production CIFS servers
• Monitor EPSS and KEV status for any change in exploit availability
• Audit CIFS multi-channel configurations to reduce unnecessary channel additions