CVE-2025-39996

UNRATEDCVSS · not yet scored
—
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • No CVSS published and no exploitation signals yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS v2: —Exploit: None knownExposed: 0

A fix is available — apply it.

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

media: b2c2: Fix use-after-free causing by irq_check_work in flexcop_pci_remove

The original code uses cancel_delayed_work() in flexcop_pci_remove(), which does not guarantee that the delayed work item irq_check_work has fully completed if it was already running. This leads to use-after-free scenarios where flexcop_pci_remove() may free the flexcop_device while irq_check_work is still active and attempts to dereference the device.

A typical race condition is illustrated below:

CPU 0 (remove) | CPU 1 (delayed work callback) flexcop_pci_remove() | flexcop_pci_irq_check_work() cancel_delayed_work() | flexcop_device_kfree(fc_pci->fc_dev) | | fc = fc_pci->fc_dev; // UAF

This is confirmed by a KASAN report:

================================================================== BUG: KASAN: slab-use-after-free in __run_timer_base.part.0+0x7d7/0x8c0 Write of size 8 at addr ffff8880093aa8c8 by task bash/135 ... Call Trace: dump_stack_lvl+0x55/0x70 print_report+0xcf/0x610 ? __run_timer_base.part.0+0x7d7/0x8c0 kasan_report+0xb8/0xf0 ? __run_timer_base.part.0+0x7d7/0x8c0 __run_timer_base.part.0+0x7d7/0x8c0 ? __pfx___run_timer_base.part.0+0x10/0x10 ? __pfx_read_tsc+0x10/0x10 ? ktime_get+0x60/0x140 ? lapic_next_event+0x11/0x20 ? clockevents_program_event+0x1d4/0x2a0 run_timer_softirq+0xd1/0x190 handle_softirqs+0x16a/0x550 irq_exit_rcu+0xaf/0xe0 sysvec_apic_timer_interrupt+0x70/0x80 ...

Allocated by task 1: kasan_save_stack+0x24/0x50 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x7f/0x90 __kmalloc_noprof+0x1be/0x460 flexcop_device_kmalloc+0x54/0xe0 flexcop_pci_probe+0x1f/0x9d0 local_pci_probe+0xdc/0x190 pci_device_probe+0x2fe/0x470 really_probe+0x1ca/0x5c0 __driver_probe_device+0x248/0x310 driver_probe_device+0x44/0x120 __driver_attach+0xd2/0x310 bus_for_each_dev+0xed/0x170 bus_add_driver+0x208/0x500 driver_register+0x132/0x460 do_one_initcall+0x89/0x300 kernel_init_freeable+0x40d/0x720 kernel_init+0x1a/0x150 ret_from_fork+0x10c/0x1a0 ret_from_fork_asm+0x1a/0x30

Freed by task 135: kasan_save_stack+0x24/0x50 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3a/0x60 __kasan_slab_free+0x3f/0x50 kfree+0x137/0x370 flexcop_device_kfree+0x32/0x50 pci_device_remove+0xa6/0x1d0 device_release_driver_internal+0xf8/0x210 pci_stop_bus_device+0x105/0x150 pci_stop_and_remove_bus_device_locked+0x15/0x30 remove_store+0xcc/0xe0 kernfs_fop_write_iter+0x2c3/0x440 vfs_write+0x871/0xd70 ksys_write+0xee/0x1c0 do_syscall_64+0xac/0x280 entry_SYSCALL_64_after_hwframe+0x77/0x7f ...

Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the delayed work item is properly canceled and any executing delayed work has finished before the device memory is deallocated.

This bug was initially identified through static analysis. To reproduce and test it, I simulated the B2C2 FlexCop PCI device in QEMU and introduced artificial delays within the flexcop_pci_irq_check_work() function to increase the likelihood of triggering the bug.

CVSS v3
—
EchelonGraph score
Not yet assessedNo source has published severity data for this CVE yet — no CVSS score from NVD or a CNA, no GitHub advisory, and it is not in CISA KEV. This is not a rating of zero; we cannot assess it yet.
EG Score
—
EG Risk
—
EPSS PROB
0%
EPSS %ILE
12%
KEV
Not listed

Published

October 15, 2025

Last Modified

April 15, 2026

References (9)

Patch Availability(25)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-virtual-hwe-20.04-edge (5.15.0.170.159) @ jammy2026-05-21ubuntu
ubuntulinux-tools-realtime-5.15 (5.15.0.1099.103) @ jammy2026-05-21ubuntu
ubuntulinux-tools-gcp-fips-5.15 (5.15.0.1100.90) @ jammy2026-05-21ubuntu
ubuntulinux-tools-aws-edge (5.15.0.1100.107~20.04.1) @ focal2026-05-21ubuntu
ubuntulinux-tools-nvidia-tegra-rt-5.15 (5.15.0.1052.52) @ jammy2026-05-21ubuntu
ubuntulinux-tools-oracle-edge (5.15.0.1097.103~20.04.1) @ focal2026-05-21ubuntu
ubuntulinux-tools-nvidia-tegra-igx-rt-5.15 (5.15.0.1041.43) @ jammy2026-05-21ubuntu
ubuntulinux-tools-nvidia-lowlatency-5.15 (5.15.0.1095.95) @ jammy2026-05-21ubuntu
ubuntulinux-tools-intel-iotg-edge (5.15.0.1095.101~20.04.1) @ focal2026-05-21ubuntu
ubuntulinux-tools-intel-iotg-5.15 (5.15.0.1095.95) @ jammy2026-05-21ubuntu
ubuntulinux-virtual-6.8 (6.8.0-106.106) @ noble2026-05-21ubuntu
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-realtime-6.8.1 (6.8.1-1045.46) @ noble2026-05-21ubuntu
ubuntulinux-tools-azure-fips-6.8 (6.8.0-1052.58+fips1) @ noble2026-05-21ubuntu
ubuntulinux-tools-raspi-nolpae (5.15.0.1097.95) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-lts-22.04 (5.15.0.1109.107) @ jammy2026-05-21ubuntu
ubuntulinux-tools-gcp-fips-6.8 (6.8.0-1052.55+fips1) @ noble2026-05-21ubuntu
ubuntulinux-tools-raspi-realtime-6.8 (6.8.0-2040.41) @ noble2026-05-21ubuntu
ubuntulinux-tools-azure-edge (6.8.0-1051.57~22.04.1) @ jammy2026-05-21ubuntu
ubuntulinux-tools-aws-edge (6.8.0-1050.53~22.04.1) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-fips-5.15 (5.15.0.1109.94) @ jammy2026-05-21ubuntu
ubuntulinux-tools-azure-edge (5.15.0.1110.119~20.04.1) @ focal2026-05-21ubuntu
ubuntulinux-xilinx-zynqmp (6.8.0.1029.30) @ noble2026-05-21ubuntu
linuxKernel @ 5.4.301—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.

All Vendor Advisories

(25)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 38× 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 134 total refreshes for this CVE.

  1. 2026-08-04 15:09 UTCEPSS rescore
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Frequently asked(4)

What is CVE-2025-39996?
CVE-2025-39996 is a publicly disclosed vulnerability published on October 15, 2025. In the Linux kernel, the following vulnerability has been resolved: media: b2c2: Fix use-after-free causing by irqcheckwork in flexcoppciremove The original code uses canceldelayedwork() in flexcoppciremove(), which does not guarantee that the delayed work item irqcheckwork has fully completed if…
When was CVE-2025-39996 disclosed?
CVE-2025-39996 was first published in the National Vulnerability Database on October 15, 2025, with the most recent update on April 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-39996 actively exploited?
CVE-2025-39996 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 87.7% of all scored CVEs.
How do I remediate CVE-2025-39996?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-39996, 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.

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