CVE-2026-98420

Received Received - Intake

ksmbd Session Expiration Logic Flaw

Publication date: 2026-10-14

Last updated on: 2026-10-19

Assigner: kernel.org

Description

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.

CVSS Scores

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Meta Information

Published

2026-10-14

Last Modified

2026-10-19

Generated

2026-10-19

AI Q&A

2026-10-15

EPSS Evaluated

2026-10-18

NVD

CVE-2026-98420

EUVD

EUVD-2026-101069

Affected Vendors & Products

Vendor	Product	Version / Range
Linux	Linux	ea174a91893956450510945a0c5d1a10b5323656
Linux	Linux	ea174a91893956450510945a0c5d1a10b5323656
Linux	Linux	a6a9601ba995d0fec635324cb9fd8d14f9bea14e
Linux	Linux	1fc8a2b14ef5223f8e0b95faba2ee0a6e4d0f99d
Linux	Linux	750a2d772e9d9ff377fd32e3b6797bf2cd847a7a
Linux	Linux	6775ee7ef4b37c521aa4cf3730f54554c4875542
Linux	Linux	5.15.145
Linux	Linux	6.1.29
Linux	Linux	6.2.16
Linux	Linux	6.3.2
Linux	Linux	6.4

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel affects the ksmbd SMB server implementation. It involves incorrect handling of SMB2 session expiration where valid sessions are destroyed after 10 seconds of inactivity when a client starts a new SessionSetup exchange. This confuses session idle time with expiration time, causing Windows clients to lose mapped drives due to invalidated tree connections.

Detection Guidance

This vulnerability is specific to the ksmbd implementation in the Linux kernel and does not provide direct detection commands. Monitoring kernel logs for session-related errors or timeouts may indicate issues. Check for mapped drive failures or STATUS_NETWORK_NAME_DELETED errors in logs.

Impact Analysis

Users relying on ksmbd for SMB file sharing may experience sudden disconnections of mapped network drives. This can disrupt file access and require users to reconnect drives manually. The issue primarily affects environments using Windows clients with Linux ksmbd servers.

Compliance Impact

The vulnerability may lead to unauthorized session termination, potentially disrupting access to shared resources and causing data access issues. This could impact compliance with GDPR by affecting data availability and integrity, and with HIPAA by compromising secure data access controls.

Mitigation Strategies

Update the Linux kernel to a patched version that resolves the ksmbd session expiration issue. Ensure the patch addresses the SMB2 session semantics and session cleanup logic. Monitor for any regressions in SMB session handling after applying updates.

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