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CVE-2025-39866

7.8 · HIGH

In the Linux kernel, the following vulnerability has been resolved: fs: writeback: fix use-after-free in __mark_inode_dirty() An use-after-free issue occurred when __mark_inode_dirty() get the bd…

Published Sep 19, 2025CWE-416EPSS 0.31%

Overview

CVE-2025-39866 is a high-severity vulnerability. It was published on September 19, 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:

fs: writeback: fix use-after-free in __mark_inode_dirty()

An use-after-free issue occurred when __mark_inode_dirty() get the

bdi_writeback that was in the progress of switching.

CPU: 1 PID: 562 Comm: systemd-random- Not tainted 6.6.56-gb4403bd46a8e #1

......

pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)

pc : __mark_inode_dirty+0x124/0x418

lr : __mark_inode_dirty+0x118/0x418

sp : ffffffc08c9dbbc0

........

Call trace:

__mark_inode_dirty+0x124/0x418

generic_update_time+0x4c/0x60

file_modified+0xcc/0xd0

ext4_buffered_write_iter+0x58/0x124

ext4_file_write_iter+0x54/0x704

vfs_write+0x1c0/0x308

ksys_write+0x74/0x10c

__arm64_sys_write+0x1c/0x28

invoke_syscall+0x48/0x114

el0_svc_common.constprop.0+0xc0/0xe0

do_el0_svc+0x1c/0x28

el0_svc+0x40/0xe4

el0t_64_sync_handler+0x120/0x12c

el0t_64_sync+0x194/0x198

Root cause is:

systemd-random-seed kworker

-----------------------

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/1edc2feb9c759a9883dfe81cb5ed231412d8b2e4Refgit.kernel.org/stable/c/b187c976111960e6e54a6b1fff724f6e3d39406cRefgit.kernel.org/stable/c/bf89b1f87c72df79cf76203f71fbf8349cd5c9deRefgit.kernel.org/stable/c/c8c14adf80bd1a6e4a1d7ee9c2a816881c26d17aRefgit.kernel.org/stable/c/d02d2c98d25793902f65803ab853b592c7a96b29Refgit.kernel.org/stable/c/e2a14bbae5d8bacaa301362744a110e2be40a3a3Refgit.kernel.org/stable/c/e63052921f1b25a836feb1500b841bff7a4a0456Reflists.debian.org/debian-lts-announce/2025/10/msg00008.htmlRefcert-portal.siemens.com/productcert/html/ssa-019113.htmlRefcert-portal.siemens.com/productcert/html/ssa-032379.html

How CyberStrike helps

Frequently asked questions

What is CVE-2025-39866?

CVE-2025-39866 is a high-severity vulnerability. It was published on September 19, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-39866?

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-2025-39866?

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-2025-39866?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-39866 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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