Unknown

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

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---

Published Aug 6, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.17%

ahead of 6% of scored CVEs · Oct 30, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ 499f377f49f085ee4aa214c738e948e88626f39b and < f41ae7e6664f3c4361129728f2c4d5f3ed995251≥ 499f377f49f085ee4aa214c738e948e88626f39b and < 210af872eafa0cf572a84cb303c0f9d2914c1226≥ 499f377f49f085ee4aa214c738e948e88626f39b and < 3d8fa4b828a86b33c60858e58aaab6df273ede05≥ 499f377f49f085ee4aa214c738e948e88626f39b and < 9c894159c5b8adc84072e3af0e55b0473a69564e≥ 499f377f49f085ee4aa214c738e948e88626f39b and < 02c903fc6fc7e16c5d1f22d18784f1208acf43e3≥ 499f377f49f085ee4aa214c738e948e88626f39b and < 7a64521802997257b144e6edfb4e278dbeb972dd≥ 499f377f49f085ee4aa214c738e948e88626f39b and < b4af31b898a948e29861cb0bae734058f9a49d9b≥ 499f377f49f085ee4aa214c738e948e88626f39b and < 1b1937eb08f51319bf71575484cde2b8c517aedc and 1 more version 4.3	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 15, 2026 → Oct 30, 2026 · 15 reading(s) · max 0.17%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 15, 2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Aug 6, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

8 on the record

git.kernel.org/stable/c/02c903fc6fc7e16c5d1f22d18784f1208acf43e3
NIST National Vulnerability Database
git.kernel.org/stable/c/9c894159c5b8adc84072e3af0e55b0473a69564e
NIST National Vulnerability Database
git.kernel.org/stable/c/1b1937eb08f51319bf71575484cde2b8c517aedc
NIST National Vulnerability Database
git.kernel.org/stable/c/b4af31b898a948e29861cb0bae734058f9a49d9b
NIST National Vulnerability Database
git.kernel.org/stable/c/210af872eafa0cf572a84cb303c0f9d2914c1226
NIST National Vulnerability Database
git.kernel.org/stable/c/7a64521802997257b144e6edfb4e278dbeb972dd
NIST National Vulnerability Database
git.kernel.org/stable/c/f41ae7e6664f3c4361129728f2c4d5f3ed995251
NIST National Vulnerability Database
git.kernel.org/stable/c/3d8fa4b828a86b33c60858e58aaab6df273ede05
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

High CVE-2026-99216 Drivers: hv: Don't reset VMBus connection state on error/exit paths 3d
Unknown CVE-2026-99215 power: supply: core: prevent unregistering a power supply while a callback runs 3d
Unknown CVE-2026-99207 scsi: target: Disable interrupts while holding delayed_cmd_lock 3d
Unknown CVE-2026-99208 drm/xe/oa: Zero OA buffer at allocation 3d
Unknown CVE-2026-99209 drm/xe: skip eviction of a BO with no resource 3d
Unknown CVE-2026-99210 accel/rocket: clear rdev on device init failure 3d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-64593 is "btrfs: do not trim a device which is not writeable", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.17% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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