CVE-2026-89788Network attack vector

Kernel use-after-free via tree-connect logoff race

Published Sep 16, 2026 · Updated Sep 16, 2026

Use-after-free in Linux ksmbd allows remote authenticated users to trigger freed-memory access by racing SMB2 tree connect with session logoff. ksmbd_tree_conn_connect() publishes a single-reference object in sess->tree_conns, and concurrent logoff frees it while smb2_tree_connect() continues initialization. The race requires an established SMB session and overlapping tree-connect and logoff operations; the observed result is a KASAN-detected slab use-after-free.

CVSS severityUnavailable
Unscored
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux ksmbd allows remote authenticated users to trigger freed-memory access by racing SMB2 tree connect with session logoff. ksmbd_tree_conn_connect() publishes a single-reference object in sess->tree_conns, and concurrent logoff frees it while smb2_tree_connect() continues initialization. The race requires an established SMB session and overlapping tree-connect and logoff operations; the observed result is a KASAN-detected slab use-after-free.

The record

CVE
CVE-2026-89788
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=33b235a6e6ebe0f05f3586a71e8d281d00f71e2e <4e30fbd26e84efa2e5cbec4eb11e126ac0c79313
  2. Affected versionversion=33b235a6e6ebe0f05f3586a71e8d281d00f71e2e <b5ec6c462aab1062cf5d1e667ba7c6442f737055
  3. Affected versionversion=5.15.145 <5.16
  4. Affected versionversion=6.1.71 <6.2
  5. Affected versionversion=6.6
  6. Affected versionversion=7b58ee8d0b91359554cf219cd4f33872ea2afd66
  7. Affected versionversion=dd45db4d9bbc8f122a9b4db5ce94ae29fcf03d3c

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=33b235a6e6ebe0f05f3586a71e8d281d00f71e2e <4e30fbd26e84efa2e5cbec4eb11e126ac0c79313; version=33b235a6e6ebe0f05f3586a71e8d281d00f71e2e <b5ec6c462aab1062cf5d1e667ba7c6442f737055; version=5.15.145 <5.16; version=6.1.71 <6.2; version=6.6; version=7b58ee8d0b91359554cf219cd4f33872ea2afd66; version=dd45db4d9bbc8f122a9b4db5ce94ae29fcf03d3c

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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