CVE-2026-90276: Linux Vulnerability

Description

In the Linux kernel, the following vulnerability has been resolved: md/md-llbitmap: stop daemon timer rearm on destroy llbitmap_destroy() deletes pending_timer before flushing md_llbitmap_io_wq. However, daemon_work can still be queued or running after the timer has been deleted, and the daemon path can arm pending_timer again when it finds dirty chunks that are not ready to flush yet. If that happens during teardown, pending_timer can remain armed after llbitmap is freed and later dereference freed memory. Add a BITMAP_SHUTDOWN bit to llbitmap->flags, set it before deleting the timer, and make the timer and daemon paths stop queueing or rearming work once teardown starts. Cancel daemon_work before flushing the shared workqueue so no already queued daemon instance can race with the free. Use timer_shutdown_sync() so a daemon instance that passed the shutdown check before teardown cannot rearm the timer afterward. BITMAP_SHUTDOWN is a runtime-only state. Mask it out when reading and updating the llbitmap superblock so the shutdown state is never loaded from disk or persisted to disk.

Metrics

EPSS Probability

0.21%

10.0th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 5ab829f1971dc99f2aac10846c378e67fc875abc, < c55aa6c17f019b6296952d336939891efa084c06; >= 5ab829f1971dc99f2aac10846c378e67fc875abc, < bb7f92d58fca9a9f06f3f51a82481c5f0bbbd46c; >= 5ab829f1971dc99f2aac10846c378e67fc875abc, < 5553d64e01d9a995be6c3de38501c6dd4ceede3b
Linux	Linux	6.18

References

Timeline

Published: Sep 17, 2026
Last Modified: Oct 19, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-90276?

In the Linux kernel, the following vulnerability has been resolved: md/md-llbitmap: stop daemon timer rearm on destroy llbitmap_destroy() deletes pending_timer before flushing md_llbitmap_io_wq. However, daemon_work can still be queued or running after the timer has been deleted, and the daemon path can arm pending_timer again when it finds dirty chunks that are not ready to flush yet. If that happens during teardown, pending_timer can remain armed after llbitmap is freed and later dereference freed memory. Add a BITMAP_SHUTDOWN bit to llbitmap->flags, set it before deleting the timer, and make the timer and daemon paths stop queueing or rearming work once teardown starts. Cancel daemon_work before flushing the shared workqueue so no already queued daemon instance can race with the free. Use timer_shutdown_sync() so a daemon instance that passed the shutdown check before teardown cannot rearm the timer afterward. BITMAP_SHUTDOWN is a runtime-only state. Mask it out when reading and updating the llbitmap superblock so the shutdown state is never loaded from disk or persisted to disk.

How severe is CVE-2026-90276?

Severity scoring for CVE-2026-90276 is pending analysis. The EPSS model estimates a 0.21% probability of exploitation in the next 30 days.

How do I fix CVE-2026-90276?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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