CVE-2026-31718Network attack vector

Kernel crash via stale ksmbd lock entries

Published May 1, 2026 · Updated May 1, 2026

Use-after-free in Linux Kernel ksmbd allows remote attackers to crash the kernel through crafted durable-handle SMB2 requests. session_fd_check() preserves a durable file handle after disconnect but leaves byte-range lock entries linked to the freed connection, and __ksmbd_close_fd() later dereferences that stale state. A reachable ksmbd share with durable handles and byte-range locks is required; guest shares can expose the path without credentials.

CVSS severity9.8
Critical
EPSS probability0.36%
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 Kernel ksmbd allows remote attackers to crash the kernel through crafted durable-handle SMB2 requests. session_fd_check() preserves a durable file handle after disconnect but leaves byte-range lock entries linked to the freed connection, and __ksmbd_close_fd() later dereferences that stale state. A reachable ksmbd share with durable handles and byte-range locks is required; guest shares can expose the path without credentials.

The record

CVE
CVE-2026-31718
Published
May 1, 2026
Updated
May 1, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-416, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 1, 2026CVE publishedPublication date reported by the CVE source.
  2. May 1, 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=6.9
  2. Affected versionversion=8df4bcdb0a4232192b2445256c39b787d58ef14d
  3. Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <235e32320a470fcd3998fb3774f2290a0eb302a1
  4. Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <3d6682726c2d3a46d31dae88b8166786b09b03ad
  5. Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9
  6. Affected versionversion=c8efcc786146a951091588e5fa7e3c754850cb3c <e33c65f011980b4ad4abfd93585ec2079856368f

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.9; version=8df4bcdb0a4232192b2445256c39b787d58ef14d; version=c8efcc786146a951091588e5fa7e3c754850cb3c <235e32320a470fcd3998fb3774f2290a0eb302a1; version=c8efcc786146a951091588e5fa7e3c754850cb3c <3d6682726c2d3a46d31dae88b8166786b09b03ad; version=c8efcc786146a951091588e5fa7e3c754850cb3c <b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9; version=c8efcc786146a951091588e5fa7e3c754850cb3c <e33c65f011980b4ad4abfd93585ec2079856368f

Published CVSS scores

9.8Linux kernel CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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-416Use After Free
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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