CVE-2026-64139

Kernel memory exhaustion via unreleased SID buffers

Published Jul 19, 2026 · Updated Jul 19, 2026

Memory leak in Linux Kernel ksmbd allows local users to exhaust kernel memory through a file with excessive POSIX ACL entries. In set_posix_acl_entries_dacl(), overflow guards break out after kmalloc_obj() allocates each smb_sid but before the matching kfree(sid). Local access to create or modify such a file and repeatedly request its DACL is required; each request leaks kernel memory until service is interrupted.

CVSS severity5.5
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in Linux Kernel ksmbd allows local users to exhaust kernel memory through a file with excessive POSIX ACL entries. In set_posix_acl_entries_dacl(), overflow guards break out after kmalloc_obj() allocates each smb_sid but before the matching kfree(sid). Local access to create or modify such a file and repeatedly request its DACL is required; each request leaks kernel memory until service is interrupted.

The record

CVE
CVE-2026-64139
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-401, T1499.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 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=299f962c0b02d048fb45d248b4da493d03f3175d <af92ee994cc7f7e83a41c2025f32257a2f82a7ef
  2. Affected versionversion=41e53a773db6342ac9a689ee5ba635c31744c9f0
  3. Affected versionversion=5e7b8f3c539d69b2ed5f2408e2f75e68ce7eef43 <0e198f09cb2a554c04de0fea4e790f1250a943ca
  4. Affected versionversion=6.1.175 <6.2
  5. Affected versionversion=6.12.84 <6.12.92
  6. Affected versionversion=6.18.25 <6.18.34
  7. Affected versionversion=6.6.136 <6.6.142
  8. Affected versionversion=7.0.2 <7.0.11
  9. Affected versionversion=8d5729350b236896f51379588d9a690b7fafb8db <9d378e17c864da08c3a4df41dae92cfa6468b00a
  10. Affected versionversion=e1955a94b6f17f4b058afa955a6f187eb3ed7615 <519fb0a42ce5d7e46935577309fb282a5f2c6ea3
  11. Affected versionversion=ef7902be3f215b6bf7babe4dc9dd9a7d57dad7a7 <eced48cb08f07393a5ea770fdd1026452883c3ad

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=299f962c0b02d048fb45d248b4da493d03f3175d <af92ee994cc7f7e83a41c2025f32257a2f82a7ef; version=41e53a773db6342ac9a689ee5ba635c31744c9f0; version=5e7b8f3c539d69b2ed5f2408e2f75e68ce7eef43 <0e198f09cb2a554c04de0fea4e790f1250a943ca; version=6.1.175 <6.2; version=6.12.84 <6.12.92; version=6.18.25 <6.18.34; version=6.6.136 <6.6.142; version=7.0.2 <7.0.11; version=8d5729350b236896f51379588d9a690b7fafb8db <9d378e17c864da08c3a4df41dae92cfa6468b00a; version=e1955a94b6f17f4b058afa955a6f187eb3ed7615 <519fb0a42ce5d7e46935577309fb282a5f2c6ea3; version=ef7902be3f215b6bf7babe4dc9dd9a7d57dad7a7 <eced48cb08f07393a5ea770fdd1026452883c3ad

Published CVSS scores

5.5NVDCVSS: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.

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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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.001OS Exhaustion Flood

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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