CVE-2025-38059 btrfs: avoid NULL pointer dereference if no valid csum tree
A local attacker can cause a kernel crash via NULL pointer dereference in btrfs scrub when using the rescue=idatacsums mount option.
- 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-2025-38059?
CVE-2025-38059 is a medium-severity vulnerability in Linux kernel, published on 18 Jun 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:
btrfs: avoid NULL pointer dereference if no valid csum tree
[BUG] When trying read-only scrub on a btrfs with rescue=idatacsums mount option, it will crash with the following call trace:
BUG: kernel NULL pointer dereference, address: 0000000000000208 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page CPU: 1 UID: 0 PID: 835 Comm: btrfs Tainted: G O 6.15.0-rc3-custom+ #236 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022 RIP: 0010:btrfs_lookup_csums_bitmap+0x49/0x480 [btrfs] Call Trace: <TASK> scrub_find_fill_first_stripe+0x35b/0x3d0 [btrfs] scrub_simple_mirror+0x175/0x290 [btrfs] scrub_stripe+0x5f7/0x6f0 [btrfs] scrub_chunk+0x9a/0x150 [btrfs] scrub_enumerate_chunks+0x333/0x660 [btrfs] btrfs_scrub_dev+0x23e/0x600 [btrfs] btrfs_ioctl+0x1dcf/0x2f80 [btrfs] __x64_sys_ioctl+0x97/0xc0 do_syscall_64+0x4f/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e
[CAUSE] Mount option "rescue=idatacsums" will completely skip loading the csum tree, so that any data read will not find any data csum thus we will ignore data checksum verification.
Normally call sites utilizing csum tree will check the fs state flag NO_DATA_CSUMS bit, but unfortunately scrub does not check that bit at all.
This results in scrub to call btrfs_search_slot() on a NULL pointer and triggered above crash.
[FIX] Check both extent and csum tree root before doing any tree search.
Weakness: CWE-476
Which versions are affected by CVE-2025-38059?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-38059?
Apply the vendor's patch.
Is CVE-2025-38059 being exploited?
There is no known exploitation of CVE-2025-38059 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-63950, AZL-70292, BELL-CVE-2025-38059, DEBIAN-CVE-2025-38059, GHSA-4h2w-f3jr-93rm, ROOT-OS-DEBIAN-11-CVE-2025-38059 and 4 more.