What is CVE-2025-39823?

CVE-2025-39823 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10, affecting Linux kernel versions from 4.19 onward and patched in 5.4.298, 5.10.242, 5.15.191 and others. CVE-2025-39823 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2025-39823?

CVE-2025-39823 has a CVSS score of 7.8 out of 10, rated High severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Is there a patch available for CVE-2025-39823?

Yes, CVE-2025-39823 has been patched. Fixed versions include 5.4.298, 5.10.242, 5.15.191 and others. If you are running Linux kernel 4.19 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2025-39823 actively exploited?

CVE-2025-39823 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2025-39823

High

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: use array_index_nospec with indices that come from guest min and dest_id are guest-controlled indices. Using array_index_nospec() after the bounds checks clamps these values to mitigate speculative execution side-channels.

Package Linux Kernel

Published 2025-09-16

Last modified 2026-05-12

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

7.8

out of 10

High

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Vector string

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

Weakness type

CWE-129

CVE-2025-39823 is classified as CWE-129

See CWE-129 on MITRE CWE for full details on this weakness type.

Affected versions

Linux kernel versions 4.19 and later are affected. Fixed in 5.4.298, 5.10.242, 5.15.191, 6.1.150, 6.6.104, 6.12.45, 6.16.5, 6.17 and their respective stable series.

Affected from

≥ 4.19

Fixed in

✓ 5.4.298 5.4.x ✓ 5.10.242 5.10.x ✓ 5.15.191 5.15.x ✓ 6.1.150 6.1.x ✓ 6.6.104 6.6.x ✓ 6.12.45 6.12.x ✓ 6.16.5 6.16.x ✓ 6.17

References

The following references provide additional information about CVE-2025-39823 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

Debian Security
https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html

Mailing List Third Party Advisory
Debian Security
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html

Mailing List Third Party Advisory
Cert-Portal
https://cert-portal.siemens.com/productcert/html/ssa-032379.html
Kernel patch commit
https://git.kernel.org/stable/c/31a0ad2f60cb4816e06218b63e695eb72ce74974
Patch
Kernel patch commit
https://git.kernel.org/stable/c/33e974c2d5a82b2f9d9ba0ad9cbaabc1c8e3985f
Patch
Kernel patch commit
https://git.kernel.org/stable/c/67a05679621b7f721bdba37a5d18665d3aceb695
Patch

8 patch commits total View all on NVD

Details

CVE ID CVE-2025-39823

Severity High

CVSS score 7.8 / 10

CVSS version 3.1

Published 2025-09-16

Modified 2026-05-12

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2025-39823?

CVE-2025-39823 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 . It affects Linux kernel versions from 4.19 onward and has been patched in 5.4.298, 5.10.242, 5.15.191 and others. CVE-2025-39823 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2025-39823?

CVE-2025-39823 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Is there a patch available for CVE-2025-39823?

Yes — CVE-2025-39823 has been patched. Fixed versions include 5.4.298, 5.10.242, 5.15.191 and others. If you are running Linux kernel 4.19 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2025-39823 actively exploited?

No — CVE-2025-39823 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.