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Response snapshot Oct 30, 2026, 17:36 UTC

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VulnerabilityCVE-2026-90153

Linux kernel: ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size

In the Linux kernel, the following vulnerability has been resolved: ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size smb_check_perm_dacl() validates that the DACL fits inside the NT security descriptor, but then bounds its two ACE walks by the remaining NTSD length (acl_size) rather than the DACL's declared size (pdacl_size).

At a glance

Exploited
Not known
Severity
8.1 High (CVSS 3.1)
Chance of exploitation
0.5% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-90153 (opens a new tab)

What happened

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size

smb_check_perm_dacl() validates that the DACL fits inside the NT security descriptor, but then bounds its two ACE walks by the remaining NTSD length (acl_size) rather than the DACL's declared size (pdacl_size).

When pdacl->size is smaller than the trailing NTSD buffer, bytes after the declared DACL boundary - still inside the stored security descriptor - are parsed as ACEs during access checks. A crafted DACL can place an access-granting ACE beyond pdacl->size, and the current code accepts it during SMB2_CREATE access validation, while parse_dacl() and smb_inherit_dacl() stop at pdacl_size.

Continue reading

Bound both ACE walks by pdacl_size to match the DACL boundary semantics used elsewhere in the server.

Validation: - semantic KUnit harness shows the post-boundary ACE is selected before the fix and rejected (EACCES) after it - linux master (7.2-rc6), x86_64

Scores and how they were measured

CVSS base severity

8.1

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.5%

Scored Percentile 41.3%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2026-90153 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  5. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-90153, scored 2026-10-30. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). Linux kernel: ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size (CVE-2026-90153). https://kevwire.com/record/CVE-2026-90153

MLA

"Linux kernel: ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size (CVE-2026-90153)." KEVWire, 30 Oct. 2026, kevwire.com/record/CVE-2026-90153.

Chicago

KEVWire. "Linux kernel: ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size (CVE-2026-90153)." Last modified October 30, 2026. https://kevwire.com/record/CVE-2026-90153.

Evidence summary (plain text)

Linux kernel: ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size (Sep 17, 2026).
In the Linux kernel, the following vulnerability has been resolved:

ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size

smb_check_perm_dacl() validates that the DACL fits inside the NT
security descriptor, but then bounds its two ACE walks by the
remaining NTSD length (acl_size) rather than the DACL's declared
size (pdacl_size).

When pdacl->size is smaller than the trailing NTSD buffer, bytes
after the declared DACL boundary - still inside the stored security
descriptor - are parsed as ACEs during access checks.
CVSS 8.1 (version 3.1; evidence as of Oct 30, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-90153).
EPSS 0.5% for the following 30 days, scored Oct 30, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-90153&date=2026-10-30).
Sources:
NVD CVE-2026-90153: https://nvd.nist.gov/vuln/detail/CVE-2026-90153
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T13:06:45.042Z&lastModEndDate=2026-10-30T14:50:57.069Z&resultsPerPage=500&startIndex=500
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T12:22:16.957Z&lastModEndDate=2026-10-30T14:05:57.373Z&resultsPerPage=500&startIndex=500
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T11:45:59.009Z&lastModEndDate=2026-10-30T13:20:57.281Z&resultsPerPage=500&startIndex=500
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-90153&date=2026-10-30
Record ID: CVE-2026-90153.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 30, 2026, 14:52 UTC. Ingestion is not an independent editorial investigation.

NVD status: Received. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

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