CVE-2025-39866

HIGHNVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2025-09-22. NVD baseline CVSS 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this weekElevated
7.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.8Exploit: NoneExposed: 0

A fix is available — apply it.

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 ---------------------------------------------------------------------- ___mark_inode_dirty inode_switch_wbs_work_fn

spin_lock(&inode->i_lock); inode_attach_wb locked_inode_to_wb_and_lock_list get inode->i_wb spin_unlock(&inode->i_lock); spin_lock(&wb->list_lock) spin_lock(&inode->i_lock) inode_io_list_move_locked spin_unlock(&wb->list_lock) spin_unlock(&inode->i_lock) spin_lock(&old_wb->list_lock) inode_do_switch_wbs spin_lock(&inode->i_lock) inode->i_wb = new_wb spin_unlock(&inode->i_lock) spin_unlock(&old_wb->list_lock) wb_put_many(old_wb, nr_switched) cgwb_release old wb released wb_wakeup_delayed() accesses wb, then trigger the use-after-free issue

Fix this race condition by holding inode spinlock until wb_wakeup_delayed() finished.

CVSS v3
7.8
EG Score
7.8(medium)
EPSS
20.6%
KEV
Not listed

Published

September 19, 2025

Last Modified

July 14, 2026

Advisory Details (10)

Auto-updated May 12, 2026
⚠️ Active exploitation confirmed. Patch available.
generic🔴 Active Exploitation

SSA-082556

https://cert-portal.siemens.com/productcert/html/ssa-082556.html
generic

SSA-032379

https://cert-portal.siemens.com/productcert/html/ssa-032379.html
generic Patch Available

[SECURITY] [DLA 4328-1] linux-6.1 security update

https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
generic

fs: writeback: fix use-after-free in __mark_inode_dirty() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/e63052921f1b25a836feb1500b841bff7a4a0456
generic

fs: writeback: fix use-after-free in __mark_inode_dirty() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/e2a14bbae5d8bacaa301362744a110e2be40a3a3
generic

fs: writeback: fix use-after-free in __mark_inode_dirty() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/d02d2c98d25793902f65803ab853b592c7a96b29
generic

fs: writeback: fix use-after-free in __mark_inode_dirty() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/c8c14adf80bd1a6e4a1d7ee9c2a816881c26d17a
generic

fs: writeback: fix use-after-free in __mark_inode_dirty() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/bf89b1f87c72df79cf76203f71fbf8349cd5c9de
generic

fs: writeback: fix use-after-free in __mark_inode_dirty() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b187c976111960e6e54a6b1fff724f6e3d39406c
generic

fs: writeback: fix use-after-free in __mark_inode_dirty() - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/1edc2feb9c759a9883dfe81cb5ed231412d8b2e4

Vendor Advisories for CVE-2025-39866(4)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(22)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-tools-gcp-fips-6.8 (6.8.0-1052.55+fips1) @ noble2026-05-21ubuntu
ubuntulinux-tools-gkeop-5.15 (5.15.0.1080.79) @ jammy2026-05-21ubuntu
ubuntulinux-tools-kvm-5.15 (5.15.0.1089.85) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-lts-22.04 (5.15.0.1101.99) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-fips-5.15 (5.15.0.1101.86) @ jammy2026-05-21ubuntu
ubuntulinux-virtual-6.8 (6.8.0-106.106) @ noble2026-05-21ubuntu
ubuntulinux-tools-gcp-fips-5.15 (5.15.0.1097.87) @ jammy2026-05-21ubuntu
ubuntulinux-tools-raspi-nolpae (5.15.0.1091.89) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-edge (5.15.0.1102.111~20.04.1) @ focal2026-05-21ubuntu
ubuntulinux-tools-nvidia-lowlatency-64k-6.8 (6.8.0-1049.52.1) @ noble2026-05-21ubuntu
ubuntulinux-tools-azure-lts-24.04 (6.8.0-1051.57) @ noble2026-05-21ubuntu
ubuntulinux-tools-raspi-realtime-6.8 (6.8.0-2040.41) @ noble2026-05-21ubuntu
ubuntulinux-tools-realtime-6.8.1 (6.8.1-1045.46) @ noble2026-05-21ubuntu
ubuntulinux-tools-aws-edge (6.8.0-1050.53~22.04.1) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-edge (6.8.0-1051.57~22.04.1) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-fips-6.8 (6.8.0-1052.58+fips1) @ noble2026-05-21ubuntu
ubuntulinux-tools-realtime-5.15 (5.15.0.1096.100) @ jammy2026-05-21ubuntu
ubuntulinux-xilinx-zynqmp (6.8.0.1029.30) @ noble2026-05-21ubuntu
ubuntulinux-xilinx-zynqmp-tools-5.15.0-1061 (5.15.0-1061.65) @ jammy2026-05-21ubuntu
redhatkernel-0:5.14.0-687.5.1.el9_82026-05-19redhat
redhatkernel-0:6.12.0-211.7.1.el10_22026-05-19redhat
linuxKernel @ 5.10.247—osv

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(19)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 15× in last 7d / 52× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 110 total refreshes for this CVE.

  1. 2026-07-15 16:57 UTCEPSS rescore
  2. 2026-07-15 16:57 UTCEPSS rescore
  3. 2026-07-15 01:59 UTCEPSS rescore
  4. 2026-07-15 01:59 UTCEPSS rescore
  5. 2026-07-14 13:19 UTCNVD updateCVSS v3 → 7.8 · severity → HIGH
  6. 2026-07-14 13:11 UTCMITRE cvelistV5
  7. 2026-07-13 22:29 UTCEPSS rescore
  8. 2026-07-13 22:29 UTCEPSS rescore
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  11. 2026-07-11 08:27 UTCEPSS rescore
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  13. 2026-07-10 05:54 UTCOSV refresh
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  1. 2026-06-29 14:06 UTCEPSS rescore
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  8. 2026-06-25 13:49 UTCEPSS rescore
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  14. 2026-06-22 14:25 UTCEPSS rescore
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  16. 2026-06-21 16:10 UTCOSV refresh
  17. 2026-06-21 14:56 UTCEPSS rescore
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  19. 2026-06-21 01:59 UTCEPSS rescore
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  21. 2026-06-19 19:25 UTCEPSS rescore
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  23. 2026-06-18 17:52 UTCEPSS rescore
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  27. 2026-06-16 17:52 UTCEPSS rescore
  28. 2026-06-14 23:17 UTCEPSS rescore
  29. 2026-06-13 23:00 UTCEPSS rescore
  30. 2026-06-12 23:11 UTCEPSS rescore
  31. 2026-06-11 14:00 UTCEPSS rescore
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  41. 2026-06-05 06:10 UTCEPSS rescore
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  43. 2026-06-04 13:12 UTCEPSS rescore
  44. 2026-06-04 13:12 UTCEPSS rescore
  45. 2026-06-02 20:12 UTCEPSS rescore
  46. 2026-06-02 14:02 UTCOSV refresh
  47. 2026-06-01 13:51 UTCEPSS rescore
  48. 2026-06-01 13:51 UTCEPSS rescore
  49. 2026-05-31 22:30 UTCEPSS rescore
  50. 2026-05-31 22:30 UTCEPSS rescore
  51. 2026-05-31 00:16 UTCEPSS rescore
  52. 2026-05-29 13:44 UTCEPSS rescore
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  73. 2026-05-21 07:48 UTCEG score recompute
  74. 2026-05-21 07:48 UTCVendor advisory
  75. 2026-05-21 07:48 UTCGHSA enrichment

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCbyteReaper77/CVE-2025-39866
    First seen Sep 26, 2025

    Proof of concept for CVE-2025-39866 (UAF and race condition)

    Open source ↗

Related CVEs(same product + same vendor + same CWE)

Frequently asked(5)

What is CVE-2025-39866?
CVE-2025-39866 is a high vulnerability published on September 19, 2025. In the Linux kernel, the following vulnerability has been resolved: fs: writeback: fix use-after-free in markinodedirty() An use-after-free issue occurred when markinodedirty() get the bdi_writeback that was in the progress of switching. CPU: 1 PID: 562 Comm: systemd-random- Not tainted…
When was CVE-2025-39866 disclosed?
CVE-2025-39866 was first published in the National Vulnerability Database on September 19, 2025, with the most recent update on July 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-39866 actively exploited?
CVE-2025-39866 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 20.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-39866?
CVE-2025-39866 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2025-39866?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-39866, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2025-39866

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