Linux Kernel up to 6.17-rc5 kernfs cgroup_file_release file descriptor consumption

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6.1$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.1.152/6.6.106/6.12.47/6.16.7/6.17-rc5. It has been rated as critical. Impacted is the function cgroup_file_release of the component kernfs. Performing a manipulation results in file descriptor consumption. This vulnerability is known as CVE-2025-39881. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.1.152/6.6.106/6.12.47/6.16.7/6.17-rc5. This affects the function cgroup_file_release of the component kernfs. The manipulation with an unknown input leads to a file descriptor consumption vulnerability. CWE is classifying the issue as CWE-769. This entry has been deprecated because it was a duplicate of CWE-774. All content has been transferred to CWE-774. The impact remains unknown. The summary by CVE is:

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 monitoring 2. Disable monitoring: echo 0 > test/cgroup.pressure 3. Re-enable monitoring: echo 1 > test/cgroup.pressure The race condition occurs because: 1. When cgroup.pressure is disabled (echo 0 > cgroup.pressure), it: - Releases PSI triggers via cgroup_file_release() - Frees of->priv through kernfs_drain_open_files() 2. While epoll still holds reference to the file and continues polling 3. Re-enabling (echo 1 > cgroup.pressure) accesses freed of->priv epolling disable/enable cgroup.pressure fd=open(cpu.pressure) while(1) ... epoll_wait kernfs_fop_poll kernfs_get_active = true echo 0 > cgroup.pressure ... cgroup_file_show kernfs_show // inactive kn kernfs_drain_open_files cft->release(of); kfree(ctx); ... kernfs_get_active = false echo 1 > cgroup.pressure kernfs_show kernfs_activate_one(kn); kernfs_fop_poll kernfs_get_active = true cgroup_file_poll psi_trigger_poll // UAF ... end: close(fd) To address this issue, introduce kernfs_get_active_of() for kernfs open files to obtain active references. This function will fail if the open file has been released. Replace kernfs_get_active() with kernfs_get_active_of() to prevent further operations on released file descriptors.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2025-39881 since 04/16/2025. The exploitability is told to be difficult. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 265866 (Linux Distros Unpatched Vulnerability : CVE-2025-39881), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.153, 6.6.107, 6.12.48, 6.16.8 or 6.17-rc6 eliminates this vulnerability. Applying the patch 34d9cafd469c69ad85e6a36b4303c78382cf5c79/854baafc00c433cccbe0ab4231b77aeb9b637b77/7e64474aba78d240f7804f48f2d454dcca78b15f/ac5cda4fae8818cf1963317bb699f7f2f85b60af/3c9ba2777d6c86025e1ba4186dc5cd930e40ec5f is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (265866) and CERT Bund (WID-SEC-2025-2107). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Google Container-Optimized OS
  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • Open Source Linux Kernel
  • RESF Rocky Linux
  • Dell Secure Connect Gateway
  • IBM QRadar SIEM
  • Dell NetWorker

Productinfo

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Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.2
VulDB Meta Temp Score: 6.1

VulDB Base Score: 4.6
VulDB Temp Score: 4.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 7.8
NVD Vector: 🔒

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: File descriptor consumption
CWE: CWE-769 / CWE-400 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 265866
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2025-39881

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.153/6.6.107/6.12.48/6.16.8/6.17-rc6
Patch: 34d9cafd469c69ad85e6a36b4303c78382cf5c79/854baafc00c433cccbe0ab4231b77aeb9b637b77/7e64474aba78d240f7804f48f2d454dcca78b15f/ac5cda4fae8818cf1963317bb699f7f2f85b60af/3c9ba2777d6c86025e1ba4186dc5cd930e40ec5f

Timelineinfo

04/16/2025 CVE reserved
09/23/2025 +160 days Advisory disclosed
09/23/2025 +0 days VulDB entry created
02/16/2026 +146 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-39881 (🔒)
GCVE (CVE): GCVE-0-2025-39881
GCVE (VulDB): GCVE-100-325605
CERT Bund: WID-SEC-2025-2107 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 09/23/2025 08:36
Updated: 02/16/2026 09:39
Changes: 09/23/2025 08:36 (59), 09/28/2025 21:40 (2), 12/01/2025 19:25 (7), 01/12/2026 04:53 (1), 01/16/2026 20:50 (11), 02/09/2026 08:13 (1), 02/16/2026 09:39 (1)
Complete: 🔍
Cache ID: 216::103

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