CVE-2025-39939

Kernel memory corruption via identity-domain miscast

Published Oct 4, 2025 · Updated Oct 4, 2025

Out-of-bounds write in Linux 6.15 through 6.16.8 and 6.17-rc1 through 6.17-rc6 allows local users to corrupt kernel memory. The zpci_get_iommu_ctrs() path casts an identity iommu_domain, which has no s390_domain backing, through to_s390_domain(), yielding an invalid address that is zeroed and later read during a sysfs statistics request. Reachability requires local low-privileged access and an s390 PCI device using an identity domain; resulting kernel corruption can expose or alter data or interrupt the system.

CVSS severity7.8
High
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

Out-of-bounds write in Linux 6.15 through 6.16.8 and 6.17-rc1 through 6.17-rc6 allows local users to corrupt kernel memory. The zpci_get_iommu_ctrs() path casts an identity iommu_domain, which has no s390_domain backing, through to_s390_domain(), yielding an invalid address that is zeroed and later read during a sysfs statistics request. Reachability requires local low-privileged access and an s390 PCI device using an identity domain; resulting kernel corruption can expose or alter data or interrupt the system.

The record

CVE
CVE-2025-39939
Published
Oct 4, 2025
Updated
Oct 4, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-787, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 4, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 4, 2025Record 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=6.15
  2. Affected versionversion=64af12c6ec3afd7d44bc8b2044eee59f98059087 <17a58caf3863163c4a84a218a9649be2c8061443
  3. Affected versionversion=64af12c6ec3afd7d44bc8b2044eee59f98059087 <b3506e9bcc777ed6af2ab631c86a9990ed97b474

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.15; version=64af12c6ec3afd7d44bc8b2044eee59f98059087 <17a58caf3863163c4a84a218a9649be2c8061443; version=64af12c6ec3afd7d44bc8b2044eee59f98059087 <b3506e9bcc777ed6af2ab631c86a9990ed97b474

Published CVSS scores

7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-787Out-of-bounds Write
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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