CVE-2026-53383Network attack vector

Remote SMB service outage via invalid session reuse

Published Jul 19, 2026 · Updated Jul 19, 2026

Denial of service in Linux Kernel ksmbd allows remote attackers to wedge SMB service for all clients via crafted SMB2 traffic. smb2_check_user_session reuses an in-progress compound-request session without checking for the VALID state, so TREE_CONNECT dereferences a null session user. Network access to TCP port 445 on a host running ksmbd is sufficient; the fault disrupts the shared worker and can panic hosts configured with panic_on_oops.

CVSS severity7.5
High
EPSS probability0.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux Kernel ksmbd allows remote attackers to wedge SMB service for all clients via crafted SMB2 traffic. smb2_check_user_session reuses an in-progress compound-request session without checking for the VALID state, so TREE_CONNECT dereferences a null session user. Network access to TCP port 445 on a host running ksmbd is sufficient; the fault disrupts the shared worker and can panic hosts configured with panic_on_oops.

The record

CVE
CVE-2026-53383
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 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=5005bcb4219156f1bf7587b185080ec1da08518e <06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7
  2. Affected versionversion=5005bcb4219156f1bf7587b185080ec1da08518e <5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4
  3. Affected versionversion=5005bcb4219156f1bf7587b185080ec1da08518e <609ca17d869d04ba249e32cdcbf13c0b1c66f43c
  4. Affected versionversion=5005bcb4219156f1bf7587b185080ec1da08518e <7cad3ceaf679c55bc9946685dacafce78ce6b51a
  5. Affected versionversion=5005bcb4219156f1bf7587b185080ec1da08518e <8f0302fb691537d33ec8f668565257ea9d340ffe
  6. Affected versionversion=5005bcb4219156f1bf7587b185080ec1da08518e <d2bbbb6c55812220fee5d801c275cc267ea3cbeb
  7. Affected versionversion=5.15.121 <5.15.211
  8. Affected versionversion=6.1.36 <6.1.177
  9. Affected versionversion=6.3.10 <6.4
  10. Affected versionversion=6.4
  11. Affected versionversion=854156d12caa9d36de1cf5f084591c7686cc8a9d <fc578523a72cb8b329d32070b95898e81613cc3f
  12. Affected versionversion=d1066c1b3663401cd23c0d6e60cdae750ce00c0f
  13. Affected versionversion=eb947403518ea3d93f6d89264bb1f5416bb0c7d0 <25ff12b82a376ff5c4583102a63d2456a6b9ebb9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=5005bcb4219156f1bf7587b185080ec1da08518e <06e1f05a1dbe8bbd054c0927b17fc0a61cc8bef7; version=5005bcb4219156f1bf7587b185080ec1da08518e <5f983b864d3d473ac533b2f4f44a1bbe5dcbccf4; version=5005bcb4219156f1bf7587b185080ec1da08518e <609ca17d869d04ba249e32cdcbf13c0b1c66f43c; version=5005bcb4219156f1bf7587b185080ec1da08518e <7cad3ceaf679c55bc9946685dacafce78ce6b51a; version=5005bcb4219156f1bf7587b185080ec1da08518e <8f0302fb691537d33ec8f668565257ea9d340ffe; version=5005bcb4219156f1bf7587b185080ec1da08518e <d2bbbb6c55812220fee5d801c275cc267ea3cbeb; version=5.15.121 <5.15.211; version=6.1.36 <6.1.177; version=6.3.10 <6.4; version=6.4; version=854156d12caa9d36de1cf5f084591c7686cc8a9d <fc578523a72cb8b329d32070b95898e81613cc3f; version=d1066c1b3663401cd23c0d6e60cdae750ce00c0f; version=eb947403518ea3d93f6d89264bb1f5416bb0c7d0 <25ff12b82a376ff5c4583102a63d2456a6b9ebb9

Published CVSS scores

7.5LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application 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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