# CVE-2026-43484: mmc: core: Avoid bitfield RMW for claim/retune flags

Status: published. Published: 2026-05-13. Updated: 2026-11-06.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 6c0cedd1ef9527ef13e66875746570e76a3188a7; < 41dce4dae583a8ce06a7ebf4ce704c46a142957c (affected, git); ≥ 6c0cedd1ef9527ef13e66875746570e76a3188a7; < bb7fc2498c3bb25fa6a91f22f4760005325cfbd5 (affected, git); ≥ 6c0cedd1ef9527ef13e66875746570e76a3188a7; < 270277c2ab631044867adb1bd2f2433d3892de6e (affected, git); ≥ 6c0cedd1ef9527ef13e66875746570e76a3188a7; < 45038e03f15e992c48603fff8c6b1c9be5397ac9 (affected, git); ≥ 6c0cedd1ef9527ef13e66875746570e76a3188a7; < 0e06cc511c61cff1591e5435a207759adcc76b6d (affected, git); ≥ 6c0cedd1ef9527ef13e66875746570e76a3188a7; < d3a3caf44c8ec26f5d63dc17c1c7242effa60ebc (affected, git); ≥ 6c0cedd1ef9527ef13e66875746570e76a3188a7; < 901084c51a0a8fb42a3f37d2e9c62083c495f824 (affected, git). Source: CNA: Linux
- Linux / Linux: 4.15 (affected); ≥ 0; < 4.15 (unaffected, semver); ≥ 5.15.203; ≤ 5.15.* (unaffected, semver); ≥ 6.1.167; ≤ 6.1.* (unaffected, semver); ≥ 6.6.130; ≤ 6.6.* (unaffected, semver); ≥ 6.12.78; ≤ 6.12.* (unaffected, semver); ≥ 6.18.19; ≤ 6.18.* (unaffected, semver); ≥ 6.19.9; ≤ 6.19.* (unaffected, semver); ≥ 7.0; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.11% as of 2026-11-06; percentile 1.50%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/41dce4dae583a8ce06a7ebf4ce704c46a142957c (CNA: Linux)

- https://git.kernel.org/stable/c/bb7fc2498c3bb25fa6a91f22f4760005325cfbd5 (CNA: Linux)

- https://git.kernel.org/stable/c/270277c2ab631044867adb1bd2f2433d3892de6e (CNA: Linux)

- https://git.kernel.org/stable/c/45038e03f15e992c48603fff8c6b1c9be5397ac9 (CNA: Linux)

- https://git.kernel.org/stable/c/0e06cc511c61cff1591e5435a207759adcc76b6d (CNA: Linux)

- https://git.kernel.org/stable/c/d3a3caf44c8ec26f5d63dc17c1c7242effa60ebc (CNA: Linux)

- https://git.kernel.org/stable/c/901084c51a0a8fb42a3f37d2e9c62083c495f824 (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-43484; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-43484; retrieved 2026-11-06; source updated Not reported

Revision: 27a26a4657cd544f63e77bb48e6474bce99fd3a6936b805f966307b412d6edd4

Canonical: https://y2.dev/cve/CVE-2026-43484

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