CVE-2026-53271Network attack vector

Service interruption via ksmbd session race

Published Jun 25, 2026 · Updated Jun 25, 2026

NULL pointer dereference in Linux Kernel ksmbd allows remote authenticated users to trigger a kernel oops via an SMB2 session race. The smb2_oplock_break_noti() and smb2_lease_break_noti() paths read opinfo->conn without READ_ONCE() or a NULL check after opinfo_get_list() drops ci->m_lock, allowing concurrent SMB2 LOGOFF to clear the pointer before ksmbd_conn_r_count_inc() writes through it. The ksmbd SMB server must be running, and an authenticated client must win the race; the oops interrupts the affected kernel execution path and disrupts SMB service.

CVSS severity5.5
Medium
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Linux Kernel ksmbd allows remote authenticated users to trigger a kernel oops via an SMB2 session race. The smb2_oplock_break_noti() and smb2_lease_break_noti() paths read opinfo->conn without READ_ONCE() or a NULL check after opinfo_get_list() drops ci->m_lock, allowing concurrent SMB2 LOGOFF to clear the pointer before ksmbd_conn_r_count_inc() writes through it. The ksmbd SMB server must be running, and an authenticated client must win the race; the oops interrupts the affected kernel execution path and disrupts SMB service.

The record

CVE
CVE-2026-53271
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=6.6.32 <6.6.143
  2. Affected versionversion=6.9
  3. Affected versionversion=8df4bcdb0a4232192b2445256c39b787d58ef14d <945a86b21b40fb17183f5b27461baa6f03e2467f
  4. Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <1ff58dcfcab434ebb51649da33774fbb8e1f7b67
  5. Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <75e33deda658c1ab3a9336cbdb1436536f9b3660
  6. Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <b003086d76968298f22e7cf62239833b5a3a06b1
  7. Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <e735dbd489e3ea02be78dba991056fe1138be51e

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.6.32 <6.6.143; version=6.9; version=8df4bcdb0a4232192b2445256c39b787d58ef14d <945a86b21b40fb17183f5b27461baa6f03e2467f; version=c8efcc786146a951091588e5fa7e3c754850cb3c <1ff58dcfcab434ebb51649da33774fbb8e1f7b67; version=c8efcc786146a951091588e5fa7e3c754850cb3c <75e33deda658c1ab3a9336cbdb1436536f9b3660; version=c8efcc786146a951091588e5fa7e3c754850cb3c <b003086d76968298f22e7cf62239833b5a3a06b1; version=c8efcc786146a951091588e5fa7e3c754850cb3c <e735dbd489e3ea02be78dba991056fe1138be51e

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
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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