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CVE-2026-64593— btrfs: do not trim a device which is not writeable

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于btrfs在设备重新出现时未正确更新bdev指针，导致对不可写设备执行trim操作时触发空指针取消引用，可能导致内核崩溃。

AI Predicted 4.7 Difficulty: Moderate EPSS 0.17% · P6

Possible ATT&CK Techniques 1 AI

T1499.002 · Service Exhaustion Flood

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 499f377f49f085ee4aa214c738e948e88626f39b< f41ae7e6664f3c4361129728f2c4d5f3ed995251 affected
499f377f49f085ee4aa214c738e948e88626f39b< 210af872eafa0cf572a84cb303c0f9d2914c1226 affected
499f377f49f085ee4aa214c738e948e88626f39b< 3d8fa4b828a86b33c60858e58aaab6df273ede05 affected
499f377f49f085ee4aa214c738e948e88626f39b< 9c894159c5b8adc84072e3af0e55b0473a69564e affected
499f377f49f085ee4aa214c738e948e88626f39b< 02c903fc6fc7e16c5d1f22d18784f1208acf43e3 affected
499f377f49f085ee4aa214c738e948e88626f39b< 7a64521802997257b144e6edfb4e278dbeb972dd affected
499f377f49f085ee4aa214c738e948e88626f39b< b4af31b898a948e29861cb0bae734058f9a49d9b affected
499f377f49f085ee4aa214c738e948e88626f39b< 1b1937eb08f51319bf71575484cde2b8c517aedc affected
… +10 more rows
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I. Basic Information for CVE-2026-64593

Vulnerability Information
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Vulnerability Title
btrfs: do not trim a device which is not writeable
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: do not trim a device which is not writeable [BUG] There is a bug report that btrfs/242 can randomly fail with the following NULL pointer dereference: run fstests btrfs/242 at 2026-06-01 10:25:08 BTRFS: device fsid d4d7f234-487c-4787-88e4-47a8b68c9874 devid 1 transid 9 /dev/sdc (8:32) scanned by mount (122609) BTRFS info (device sdc): first mount of filesystem d4d7f234-487c-4787-88e4-47a8b68c9874 BTRFS info (device sdc): using crc32c checksum algorithm BTRFS warning (device sdc): devid 2 uuid fbe72d72-3272-482d-80fb-ab88ed398192 is missing BTRFS warning (device sdc): devid 2 uuid fbe72d72-3272-482d-80fb-ab88ed398192 is missing BTRFS info (device sdc): allowing degraded mounts BTRFS info (device sdc): turning on async discard BTRFS info (device sdc): enabling free space tree Unable to handle kernel NULL pointer dereference at virtual address 0000000000000018 user pgtable: 4k pages, 48-bit VAs, pgdp=000000013fd6b000 CPU: 4 UID: 0 PID: 122625 Comm: fstrim Not tainted 7.0.10-2-default #1 PREEMPT(full) openSUSE Tumbleweed e9a5f6b24978fba3bf015a992f865837fdfff3dd Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20250812-19.fc42 08/12/2025 pstate: 01400005 (nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) pc : btrfs_trim_fs+0x34c/0xa00 [btrfs] lr : btrfs_trim_fs+0x1f0/0xa00 [btrfs] Call trace: btrfs_trim_fs+0x34c/0xa00 [btrfs f02c1d570ceea621c69d302ba75dd61868083840] (P) btrfs_ioctl_fitrim+0xe8/0x178 [btrfs f02c1d570ceea621c69d302ba75dd61868083840] btrfs_ioctl+0xdd4/0x2bd8 [btrfs f02c1d570ceea621c69d302ba75dd61868083840] __arm64_sys_ioctl+0xac/0x108 invoke_syscall.constprop.0+0x5c/0xd0 el0_svc_common.constprop.0+0x40/0xf0 do_el0_svc+0x24/0x40 el0_svc+0x40/0x1d0 el0t_64_sync_handler+0xa0/0xe8 el0t_64_sync+0x1b0/0x1b8 Code: 17ffff83 f94017e0 f9002be0 f9402ea0 (f9400c00) ---[ end trace 0000000000000000 ]--- Also the reporter is very kind to test the following ASSERT() added to btrfs_trim_free_extents_throttle(): ASSERT(device->bdev, "devid=%llu path=%s dev_state=0x%lx\n", device->devid, btrfs_dev_name(device), device->dev_state); And it shows the following output: assertion failed: device->bdev, in extent-tree.c:6630 (devid=2 path=/dev/sdd dev_state=0x82) Which means the device->bdev is NULL, and the dev_state is BTRFS_DEV_STATE_IN_FS_METADATA | BTRFS_DEV_STATE_ITEM_FOUND, without BTRFS_DEV_STATE_WRITEABLE flag set. [CAUSE] The pc points to the following call chain: btrfs_trim_fs() |- btrfs_trim_free_extents() |- btrfs_trim_free_extents_throttle() |- bdev_max_discard_sectors(device->bdev) So the NULL pointer dereference is caused by device->bdev being NULL. This looks impossible by a quick glance, as just before calling btrfs_trim_free_extents_throttle(), we have skipped any device that has BTRFS_DEV_STATE_MISSING flag set. However in this particular case, there is a window where the missing device is later re-scanned, causing btrfs to remove the BTRFS_DEV_STATE_MISSING flag: btrfs_control_ioctl() |- btrfs_scan_one_device() |- device_list_add() |- rcu_assign_pointer(device->name, name); | This updates the missing device's path to the new good path. | |- clear_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state) This removes the BTRFS_DEV_STATE_MISSING flag. This allows the missing device to re-appear and clear the BTRFS_DEV_STATE_MISSING flag. However the device still does not have the BTRFS_DEV_STATE_WRITEABLE flag set, nor is its bdev pointer updated. The bdev pointer remains NULL, triggering the crash later. [FIX] This is a big de-synchronization between BTRFS_DEV_STATE_MISSING and device->bdev pointer, and shows a gap in btrfs's re-appearing-device handling. The proper handling of re-appearing device will need quite some extra work, which is out of the context of this small ---truncated---
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于btrfs在设备重新出现时未正确更新bdev指针，导致对不可写设备执行trim操作时触发空指针取消引用，可能导致内核崩溃。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 499f377f49f085ee4aa214c738e948e88626f39b ~ f41ae7e6664f3c4361129728f2c4d5f3ed995251 -
Linux Linux 4.3 -

II. Public POCs for CVE-2026-64593

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III. Intelligence Information for CVE-2026-64593

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Patches & Fixes for CVE-2026-64593 (8)

Same Patch Batch · Linux · 2026-08-06 · 22 CVEs total

CVE-2026-64597 9.8 CRITICAL smb: client: fix double-free in SMB2_close() replay
CVE-2026-64586 8.8 HIGH wifi: brcmfmac: drain bus_reset work on device removal
CVE-2026-64598 8.8 HIGH smb/client: Fix error code in smb2_aead_req_alloc()
CVE-2026-64584 7.8 HIGH usb: gadget: f_midi: cancel pending IN work before freeing the midi object
CVE-2026-64585 7.8 HIGH can: esd_usb: kill anchored URBs before freeing netdevs
CVE-2026-64588 7.8 HIGH fuse-uring: fix data races on ring->ready
CVE-2026-64583 7.8 HIGH usb: gadget: udc: bdc: free IRQ and drain func_wake_notify before teardown
CVE-2026-64601 7.8 HIGH ALSA: us144mkii: capture_urb_complete: redundant usb_anchor_urb corrupts anchor list on ea
CVE-2026-64599 7.8 HIGH crypto: amlogic - avoid double cleanup in meson_crypto_probe()
CVE-2026-64587 7.0 HIGH net: ethernet: arc: emac: quiesce interrupts before requesting IRQ
CVE-2026-68480 x86/bugs: Make Safe-RET robust against interrupt injection
CVE-2026-64604 KVM: VMX: Grab vmcs12 on CR8 interception update iff vCPU is in guest mode
CVE-2026-64603 platform/x86: intel-hid: Protect ACPI notify handler against recursion
CVE-2026-64602 iio: adc: spear: Initialize completion before requesting IRQ
CVE-2026-64596 libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()
CVE-2026-64595 HID: hid-lenovo-go: cancel cfg_setup work in hid_go_cfg_remove()
CVE-2026-64594 usb: gadget: f_fs: initialize reset_work at allocation time
CVE-2026-64592 riscv: mm: Unconditionally sfence.vma for spurious fault
CVE-2026-64591 iommu/vt-d: Avoid WARNING in sva unbind path
CVE-2026-64590 dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning

Showing top 20 of 22 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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