CVE-2025-39836

Local kernel corruption via noncontiguous STMM buffer

Published Sep 16, 2025 · Updated Sep 16, 2025

Memory corruption in the Linux kernel allows local users to alter kernel memory by reading EFI variable files through efivarfs. setup_mm_hdr() allocates the STMM communication buffer with kmalloc(), but tee_shm_register_kernel_buf() treats it as contiguous pages and releases slab-backed pages incorrectly. Access to efivarfs and a kernel built with the EFI STMM driver is required; a crafted variable read can corrupt adjacent kernel objects, crash the host, or support privilege escalation.

CVSS severity7.8
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in the Linux kernel allows local users to alter kernel memory by reading EFI variable files through efivarfs. setup_mm_hdr() allocates the STMM communication buffer with kmalloc(), but tee_shm_register_kernel_buf() treats it as contiguous pages and releases slab-backed pages incorrectly. Access to efivarfs and a kernel built with the EFI STMM driver is required; a crafted variable read can corrupt adjacent kernel objects, crash the host, or support privilege escalation.

The record

CVE
CVE-2025-39836
Published
Sep 16, 2025
Updated
Sep 16, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.8
  2. Affected versionversion=c44b6be62e8dd4ee0a308c36a70620613e6fc55f <630c0e6064daf84f17aad1a7d9ca76b562e3fe47
  3. Affected versionversion=c44b6be62e8dd4ee0a308c36a70620613e6fc55f <77ff27ff0e4529a003c8a1c2492c111968c378d3
  4. Affected versionversion=c44b6be62e8dd4ee0a308c36a70620613e6fc55f <c5e81e672699e0c5557b2b755cc8f7a69aa92bff

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.8; version=c44b6be62e8dd4ee0a308c36a70620613e6fc55f <630c0e6064daf84f17aad1a7d9ca76b562e3fe47; version=c44b6be62e8dd4ee0a308c36a70620613e6fc55f <77ff27ff0e4529a003c8a1c2492c111968c378d3; version=c44b6be62e8dd4ee0a308c36a70620613e6fc55f <c5e81e672699e0c5557b2b755cc8f7a69aa92bff

Published CVSS scores

5.5SUSECVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
5.5Amazon LinuxCVSS: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

T1068Exploitation for Privilege Escalation

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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