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

> An unauthenticated remote attacker can cause denial of service in the Linux kernel ksmbd server by triggering premature session expiration and resource exhaustion.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-110456, BELL-CVE-2026-98420, DEBIAN-CVE-2026-98420, GHSA-h7rp-r63v-fmfm, UBUNTU-CVE-2026-98420

## What is CVE-2026-98420?

CVE-2026-98420 is a denial of service vulnerability in Linux, published on 14 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2026-98420?


## How do I fix CVE-2026-98420?

Apply the vendor's patch.

## Is CVE-2026-98420 being exploited?

There is no known exploitation of CVE-2026-98420 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98420 and fix it if it is affected.

What it is: CVE-2026-98420 is a denial of service vulnerability in Linux, published on 14 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98420 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98420/ (Markdown: https://insights.sbomify.com/CVE-2026-98420/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98420
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98420
- OSV: https://osv.dev/vulnerability/CVE-2026-98420

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98420/
Summaries are generated and may contain mistakes; the official description above is the record.