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CVE-2026-89998
dm: fix race when loading and unloading a table
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem drivers/md. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89998 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
If the userspace calls two concurrent table load ioctls and one of them succeeds and the other fails, there is a race condition because dm_setup_md_queue walks &md->table_devices without any lock. If the walk races with dm_table_destroy -> free_devices -> dm_put_table_device, there is access to invalid memory. Fix this race by extending the lock over the list walk.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/md/dm.c
- What this is
- DEVICE-MAPPER (LVM)MAINTAINERS section matched on drivers/md/dm* · dm-devel@lists.linux.dev · Maintained
- Kernel module
- dm_mod
Check it on the machine
grep -wE 'CONFIG_BLK_DEV_DM|CONFIG_MD' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w dm_modPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switches
- CONFIG_BLK_DEV_DM, CONFIG_MD
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-16 (33 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/md
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.1.2 | 6.1.188 | b02e35b81176 |
| 6.2 | 6.6.157 | 0ea6e5ad4a58 |
| 6.2 | 6.12.110 | a1af1884c960 |
| 6.2 | 6.18.51 | af1f32ccf805 |
| 6.2 | 7.2.5 | 00ad6f9ed27f |
| 6.2 | 7.3 | 5380c7f6335c |
| 6.0.16 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The race is reached only through local DM_TABLE_LOAD ioctls on /dev/mapper/control (ctl_ioctl → table_load → dm_setup_md_queue walking md->table_devices). No network, Bluetooth, or physical-bus path loads a device-mapper table.
- AC:LAttack complexity, low
- The attacker issues two concurrent table-load ioctls on a mapped device they created, owning both sides of the race: one load fails after populate_table added devices and dm_table_destroy frees them while the other walks the list. Device-mapper is a standard distro component, not a rare config.
- PR:LPrivileges required, low
- ctl_ioctl requires capable(CAP_SYS_ADMIN). In the most severe reasonable deployment that capability is held by a container, CSI, or LVM/storage-stack administrator with delegated /dev/mapper/control rather than exclusive host root, matching kernel-CNA scoring of other device-mapper ioctl bugs as Low.
- UI:NUser interaction, none
- The attacker performs every step with its own ioctls (DM_DEV_CREATE then concurrent DM_TABLE_LOAD). No separate victim action such as mounting a filesystem or opening a file is required.
- S:UScope, unchanged
- The use-after-free of struct table_device stays inside the host kernel's security authority. This is standard kernel memory corruption, not a VM, IOMMU, or sandbox boundary crossing.
- C:HConfidentiality impact, high
- dm_setup_md_queue walks md->table_devices and dereferences td->dm_dev.bdev after a concurrent dm_table_destroy has kfree'd the table_device. Reclaiming that slab object yields an arbitrary kernel read, so confidentiality is High.
- I:HIntegrity impact, high
- The same use-after-free lets an attacker spray a replacement object so bd_link_disk_holder writes through an attacker-controlled bdev pointer, a classic heap UAF write and control-flow hijack primitive, so integrity is High.
- A:HAvailability impact, high
- Walking a freed table_device list entry or calling bd_link_disk_holder on a dangling bdev causes a kernel oops, panic, or hang, which is a complete availability impact.