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CVE-2025-39881

7.8 · HIGH

In the Linux kernel, the following vulnerability has been resolved: kernfs: Fix UAF in polling when open file is released A use-after-free (UAF) vulnerability was identified in the PSI (Pressure…

Published Sep 23, 2025CWE-416EPSS 0.15%

Overview

CVE-2025-39881 is a high-severity vulnerability. It was published on September 23, 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:

kernfs: Fix UAF in polling when open file is released

A use-after-free (UAF) vulnerability was identified in the PSI (Pressure

Stall Information) monitoring mechanism:

BUG: KASAN: slab-use-after-free in psi_trigger_poll+0x3c/0x140

Read of size 8 at addr ffff3de3d50bd308 by task systemd/1

psi_trigger_poll+0x3c/0x140

cgroup_pressure_poll+0x70/0xa0

cgroup_file_poll+0x8c/0x100

kernfs_fop_poll+0x11c/0x1c0

ep_item_poll.isra.0+0x188/0x2c0

Allocated by task 1:

cgroup_file_open+0x88/0x388

kernfs_fop_open+0x73c/0xaf0

do_dentry_open+0x5fc/0x1200

vfs_open+0xa0/0x3f0

do_open+0x7e8/0xd08

path_openat+0x2fc/0x6b0

do_filp_open+0x174/0x368

Freed by task 8462:

cgroup_file_release+0x130/0x1f8

kernfs_drain_open_files+0x17c/0x440

kernfs_drain+0x2dc/0x360

kernfs_show+0x1b8/0x288

cgroup_file_show+0x150/0x268

cgroup_pressure_write+0x1dc/0x340

cgroup_file_write+0x274/0x548

Reproduction Steps:

1. Open test/cpu.pressure and establish epoll

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/34d9cafd469c69ad85e6a36b4303c78382cf5c79Refgit.kernel.org/stable/c/3c9ba2777d6c86025e1ba4186dc5cd930e40ec5fRefgit.kernel.org/stable/c/7e64474aba78d240f7804f48f2d454dcca78b15fRefgit.kernel.org/stable/c/854baafc00c433cccbe0ab4231b77aeb9b637b77Refgit.kernel.org/stable/c/ac5cda4fae8818cf1963317bb699f7f2f85b60afReflists.debian.org/debian-lts-announce/2025/10/msg00008.html

How CyberStrike helps

Frequently asked questions

What is CVE-2025-39881?

CVE-2025-39881 is a high-severity vulnerability. It was published on September 23, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).

How severe is CVE-2025-39881?

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-2025-39881?

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-2025-39881?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-39881 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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