CVE-2026-43484 mmc: core: Avoid bitfield RMW for claim/retune flags
A race condition in the Linux kernel MMC core allows concurrent updates to corrupt shared bitfields, potentially triggering warnings and causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43484?
CVE-2026-43484 is a medium-severity vulnerability in Linux kernel, published on 13 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-43484?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43484?
Apply the vendor's patch.
Is CVE-2026-43484 being exploited?
There is no known exploitation of CVE-2026-43484 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43484, DEBIAN-CVE-2026-43484, GHSA-42p4-9577-4wfh, ROOT-OS-DEBIAN-11-CVE-2026-43484, ROOT-OS-UBUNTU-2204-CVE-2026-43484, ROOT-OS-UBUNTU-2404-CVE-2026-43484 and 1 more.