CVE-2025-38059
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk9th percentile - higher than 9% of all known CVEs
Summary
In the Linux kernel, a NULL pointer dereference vulnerability exists in btrfs when performing a read-only scrub on a filesystem mounted with the rescue=idatacsums option. This option skips loading the checksum tree, and scrub does not check the NO_DATA_CSUMS flag, leading to a call to btrfs_search_slot() on a NULL pointer and a kernel crash.
Risk Assessment
A local user could exploit this flaw to trigger a kernel crash (denial of service) by initiating a scrub on a btrfs filesystem mounted with the rescue=idatacsums option. In multi-user environments, this may lead to system instability.
Recommendation
Update the Linux kernel to a version containing the fix (the patch checks both extent and csum tree roots before any tree search). Until patched, avoid running scrub on btrfs filesystems mounted with rescue=idatacsums.
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- CVE-2026-99247Unknown
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

