CVE-2026-31611Network attack vector

File permission alteration via truncated SID

Published Apr 24, 2026 · Updated Apr 24, 2026

Out-of-bounds read in Linux Kernel ksmbd allows remote attackers to alter file permissions via a crafted SMB2 security descriptor. In parse_dacl(), compare_sids() accepts a two-sub-authority S-1-5-88-3 SID as a match, then reads the absent sub_auth[2] four bytes beyond the ACL and masks it into mode bits. A reachable ksmbd SMB share is required; guest-enabled writable shares expose the path without credentials, and the result is constrained permission changes, limited data exposure, or a kernel crash.

CVSS severity8.6
High
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Linux Kernel ksmbd allows remote attackers to alter file permissions via a crafted SMB2 security descriptor. In parse_dacl(), compare_sids() accepts a two-sub-authority S-1-5-88-3 SID as a match, then reads the absent sub_auth[2] four bytes beyond the ACL and masks it into mode bits. A reachable ksmbd SMB share is required; guest-enabled writable shares expose the path without credentials, and the result is constrained permission changes, limited data exposure, or a kernel crash.

The record

CVE
CVE-2026-31611
Published
Apr 24, 2026
Updated
Apr 24, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1222.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 24, 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <08f9e6d899b5c834bbcc239eae1bed58d9b15d2c
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <46bbcd3ebfb3549c8da1838fc4493e79bd3241e7
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d2454f4a002d08560a60f214f392e6491cf11560

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <08f9e6d899b5c834bbcc239eae1bed58d9b15d2c; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <46bbcd3ebfb3549c8da1838fc4493e79bd3241e7; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9401f86a224f37b50e6a3ccf1d46a70d5ef8af0a; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d2454f4a002d08560a60f214f392e6491cf11560

Published CVSS scores

8.6kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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

T1222.002Linux and Mac File and Directory Permissions Modification

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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