Cloudanix VulnDB

CVE-2026-98420

None

CVSS

—

EPSS

0.2%

Published

Oct 14, 2026

CISA due date

—

Cloudanix analysis

Schedule a fix SSVC: Track

A bug in Linux file-sharing software can cause connected network drives to suddenly stop working when a client tries to open another session.

Exploitation
Remote Unauthenticated
Attacker needs
None
Complexity
Low
Impact
Denial Of Service
Component
OS kernel
Class
Other
Remediation
Patch
Effort
Medium
Patch risk
Low

What it actually does

The ksmbd module incorrectly destroys valid SMB sessions after ten seconds of inactivity on additional SessionSetup requests by conflating Session.IdleTime with Session.ExpirationTime, invalidating tree connects and returning STATUS_NETWORK_NAME_DELETED to clients.

Why it matters to the business

Mapped network drives and SMB file shares on Linux servers can abruptly fail, interrupting user access to shared resources and requiring manual reconnection or service restarts until the server is updated.

How an attack unfolds

An attacker establishes an SMB connection, authenticates a session, then issues additional SessionSetup exchanges; the server prematurely expires the prior valid session, breaking its tree connects and mapped drives without requiring authentication bypass or code execution.

How to fix it

Upgrade the Linux kernel to a version containing the ksmbd session expiration fix that enforces Windows-compatible 45-second timeouts, preserves valid or expired sessions until credential expiration, and correctly handles InProgress re-authentication states.

How to confirm the fix worked

Confirm the running kernel contains the referenced ksmbd patch, then exercise multiple SessionSetup exchanges on an established connection and verify that the original session and its tree connects remain intact.

Typical attack path

  1. Establish a TCP or SMB Direct connection to the ksmbd server
  2. Complete initial SessionSetup to create a valid session with tree connects
  3. Issue one or more additional SessionSetup requests within the ten-second window
  4. Trigger the flawed session register logic that deletes the older valid session
  5. Observe STATUS_NETWORK_NAME_DELETED errors and loss of mapped drive functionality

How to detect it

Inspect ksmbd and SMB server logs for unexpected valid-session deletions, STATUS_NETWORK_NAME_DELETED errors on active sessions, or repeated SessionSetup activity followed by session loss.

What your security team should do

  • Prioritize kernel updates for all systems running ksmbd
  • Review SMB server logs for repeated session teardown events
  • Test SMB client reconnection behavior after applying updates

The record

In the Linux kernel, the following vulnerability has been resolved: ksmbd: follow SMB2 session expiration semantics ksmbd_session_register() destroys valid sessions after ten seconds of inactivity whenever a client starts another SessionSetup exchange. This confuses Session.IdleTime with Session.ExpirationTime. Windows can create additional authenticated sessions on an existing connection, so deleting the older session invalidates its tree connects and makes mapped drives fail with STATUS_NETWORK_NAME_DELETED. The session expiration rules require the server to change a valid session to expired only after its credential expiration time passes. A valid or expired session otherwise keeps its connection from being scavenged. Connections that have not negotiated a dialect, have no sessions, or have only InProgress sessions are disconnected after an implementation-specific timeout. Use the Windows-compatible 45 second value and run the expiration check periodically for both TCP and SMB Direct. Keep zero as an infinite credential expiration time, and count each Valid-to-Expired transition. Set expired sessions to InProgress when they reauthenticate. If authentication fails, remove the session from the global and per-connection tables immediately, including SMB3 multichannel connections. Retain protection against abandoned SessionId-zero exchanges by allowing only one InProgress authentication per connection. Additional exchanges fail with STATUS_INSUFFICIENT_RESOURCES, and stale InProgress sessions are reaped after the same 45 second setup timeout. This bounds the original unauthenticated memory-exhaustion path without evicting established sessions.

Affected packages

Ecosystem Package Introduced Fixed