# CVE-2026-98420: ksmbd: follow SMB2 session expiration semantics

CVE-2026-98420 is fixed in linux on 1 platform by DEBIAN-CVE-2026-98420 (version 7.2.8-1), released October 16, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-98420
- Priority: Routine
- CVSS: 5.5 (Moderate)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 14, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98420

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.2.8-1 | [DEBIAN-CVE-2026-98420](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98420.md) | Oct 16, 2026 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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