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CVE-2025-40040

7.8 · HIGH

In the Linux kernel, the following vulnerability has been resolved: mm/ksm: fix flag-dropping behavior in ksm_madvise syzkaller discovered the following crash: (kernel BUG) [ 44.607039] ------…

Published Oct 28, 2025EPSS 0.38%

Overview

CVE-2025-40040 is a high-severity vulnerability. It was published on October 28, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

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

mm/ksm: fix flag-dropping behavior in ksm_madvise

syzkaller discovered the following crash: (kernel BUG)

[ 44.607039] ------------[ cut here ]------------

[ 44.607422] kernel BUG at mm/userfaultfd.c:2067!

[ 44.608148] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI

[ 44.608814] CPU: 1 UID: 0 PID: 2475 Comm: reproducer Not tainted 6.16.0-rc6 #1 PREEMPT(none)

[ 44.609635] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014

[ 44.610695] RIP: 0010:userfaultfd_release_all+0x3a8/0x460

<snip other registers, drop unreliable trace>

[ 44.617726] Call Trace:

[ 44.617926] <TASK>

[ 44.619284] userfaultfd_release+0xef/0x1b0

[ 44.620976] __fput+0x3f9/0xb60

[ 44.621240] fput_close_sync+0x110/0x210

[ 44.622222] __x64_sys_close+0x8f/0x120

[ 44.622530] do_syscall_64+0x5b/0x2f0

[ 44.622840] entry_SYSCALL_64_after_hwfram

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/41cb9fd904fe0c39d52e82dd84dc3c96b7aa9693Refgit.kernel.org/stable/c/76385629f45740b7888f8fcd83bde955b10f61feRefgit.kernel.org/stable/c/788e5385d0ff69cdba1cabccb9dab8d9647b9239Refgit.kernel.org/stable/c/850f1ea245bdc0ce6a3fd36bfb80d8cf9647cb71Refgit.kernel.org/stable/c/92b82e232b8d8b116ac6e57aeae7a6033db92c60Refgit.kernel.org/stable/c/ac50c6e0a8f91a02b681af81abb2362fbb67cc18Refgit.kernel.org/stable/c/b69f19244c2b6475c8a6eb72f0fb0d53509e48cdRefgit.kernel.org/stable/c/f04aad36a07cc17b7a5d5b9a2d386ce6fae63e93

How CyberStrike helps

Frequently asked questions

What is CVE-2025-40040?

CVE-2025-40040 is a high-severity vulnerability. It was published on October 28, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-40040?

This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2025-40040?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-40040?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-40040 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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