CVE-2025-21712 md/md-bitmap: Synchronize bitmap_get_stats() with bitmap lifetime

High 7.8 Published 27 Feb 2025 Updated 15 Oct 2026

A local attacker can crash the Linux kernel by triggering a null pointer dereference in the md bitmap subsystem during status reads.

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-2025-21712?

CVE-2025-21712 is a high-severity vulnerability in Linux kernel, published on 27 Feb 2025. 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:

md/md-bitmap: Synchronize bitmap_get_stats() with bitmap lifetime

After commit ec6bb299c7c3 ("md/md-bitmap: add 'sync_size' into struct md_bitmap_stats"), following panic is reported:

Oops: general protection fault, probably for non-canonical address RIP: 0010:bitmap_get_stats+0x2b/0xa0 Call Trace: <TASK> md_seq_show+0x2d2/0x5b0 seq_read_iter+0x2b9/0x470 seq_read+0x12f/0x180 proc_reg_read+0x57/0xb0 vfs_read+0xf6/0x380 ksys_read+0x6c/0xf0 do_syscall_64+0x82/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Root cause is that bitmap_get_stats() can be called at anytime if mddev is still there, even if bitmap is destroyed, or not fully initialized. Deferenceing bitmap in this case can crash the kernel. Meanwhile, the above commit start to deferencing bitmap->storage, make the problem easier to trigger.

Fix the problem by protecting bitmap_get_stats() with bitmap_info.mutex.

Which versions are affected by CVE-2025-21712?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21712?

Apply the vendor's patch.

Is CVE-2025-21712 being exploited?

There is no known exploitation of CVE-2025-21712 in the wild and no public exploit code.

All Linux kernel vulnerabilities

Sources

Also known as AZL-68763, BELL-CVE-2025-21712, DEBIAN-CVE-2025-21712, GHSA-vq63-h845-wgm6, ROOT-OS-DEBIAN-11-CVE-2025-21712, ROOT-OS-UBUNTU-2204-CVE-2025-21712 and 2 more.