CVE-2026-43484
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
In the Linux kernel, a vulnerability was found in the MMC subsystem where the 'claimed' and 'retune' control flags shared the same bitfield word. Concurrent writes in asynchronous contexts could overwrite other bits, causing spurious WARN_ON(!host->claimed) warnings. The fix converts these flags to bool type, eliminating unintended read-modify-write (RMW) side effects.
Risk Assessment
The vulnerability may cause system instability, false alarms, and potential disruptions in MMC controller operation, which in production environments could lead to data loss or service failure.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit removing bitfield sharing for 'claimed' and 'retune' flags). Monitor official security advisories from your Linux distribution.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: mmc: core: Avoid bitfield RMW for claim/retune flags Move claimed and retune control flags out of the bitfield word to avoid unrelated RMW side effects in asynchronous contexts. The host->claimed bit shared a word with retune flags. Writes to claimed in __mmc_claim_host() or retune_now in mmc_mq_queue_rq() can overwrite other bits when concurrent updates happen in other contexts, triggering spurious WARN_ON(!host->claimed). Convert claimed, can_retune, retune_now and retune_paused to bool to remove shared-word coupling.