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Response snapshot Oct 31, 2026, 14:16 UTC

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VulnerabilityCVE-2026-99110

Linux kernel: smb: client: fix heap overflow in cifs_do_set_acl()

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix heap overflow in cifs_do_set_acl() cifs_set_acl() validates ACL size using posix_acl_xattr_size(): 4 + (count * 8) // 4-byte header + 8 bytes per ACE cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS wire format into the same buffer: 6 + (count * 10) // 6-byte header + 10 bytes per ACE An ACL that passes the xattr-based check in cifs_set_acl() can overflow the heap when posix_acl_to_cifs() writes the larger CIFS format.

At a glance

Exploited
Not known
Severity
7.0 High (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-99110 (opens a new tab)

What happened

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

smb: client: fix heap overflow in cifs_do_set_acl()

cifs_set_acl() validates ACL size using posix_acl_xattr_size():

4 + (count * 8) // 4-byte header + 8 bytes per ACE

Continue reading

cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS wire format into the same buffer:

6 + (count * 10) // 6-byte header + 10 bytes per ACE

An ACL that passes the xattr-based check in cifs_set_acl() can overflow the heap when posix_acl_to_cifs() writes the larger CIFS format.

Validate the CIFS format size against the remaining buffer space and USHRT_MAX before converting--data_count is __u16, so sizes above USHRT_MAX truncate the on-wire packet length, causing the server to apply a partial ACL. Replace MaxDataCount = 1000 with min(CIFSMaxBufSize, USHRT_MAX).

Scores and how they were measured

CVSS base severity

7.0

Version 3.1As of

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

Measurement source (opens a new tab)

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

EPSS probability

Not available

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-2026-99110 (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

Cite this record

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

APA

KEVWire. (2026, October 31). Linux kernel: smb: client: fix heap overflow in cifs_do_set_acl() (CVE-2026-99110). https://kevwire.com/record/CVE-2026-99110

MLA

"Linux kernel: smb: client: fix heap overflow in cifs_do_set_acl() (CVE-2026-99110)." KEVWire, 31 Oct. 2026, kevwire.com/record/CVE-2026-99110.

Chicago

KEVWire. "Linux kernel: smb: client: fix heap overflow in cifs_do_set_acl() (CVE-2026-99110)." Last modified October 31, 2026. https://kevwire.com/record/CVE-2026-99110.

Evidence summary (plain text)

Linux kernel: smb: client: fix heap overflow in cifs_do_set_acl() (Oct 28, 2026).
In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix heap overflow in cifs_do_set_acl()

cifs_set_acl() validates ACL size using posix_acl_xattr_size():

        4 + (count * 8)  // 4-byte header + 8 bytes per ACE

cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS
wire format into the same buffer:

        6 + (count * 10)  // 6-byte header + 10 bytes per ACE

An ACL that passes the xattr-based check in cifs_set_acl() can
overflow the heap when posix_acl_to_cifs() writes the larger CIFS
format.
CVSS 7.0 (version 3.1; evidence as of Oct 31, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-99110).
Sources:
NVD CVE-2026-99110: https://nvd.nist.gov/vuln/detail/CVE-2026-99110
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-31T12:40:58.114Z&lastModEndDate=2026-10-31T14:15:57.636Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-31T10:50:56.512Z&lastModEndDate=2026-10-31T13:40:56.165Z&resultsPerPage=500&startIndex=0
Record ID: CVE-2026-99110.
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 31, 2026, 14:15 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

Record detail