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CVE-2026-72103
dm: avoid leaking the caller's thread keyring via the table device file
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem drivers/md. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72103 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The refactoring in commit a28d893eb327 ("md: port block device access to file") accidentally causes the caller's thread keyring to be kept alive long beyond the caller's lifetime. As a result, "cryptsetup luksSuspend" silently fails to wipe the LUKS volume key from memory. In detail: "cryptsetup luksOpen" uses its supposedly ephemeral thread keyring to pass the volume key to the kernel. dm-crypt's crypt_set_keyring_key() copies the key material into its own crypt_config structure and then drops its own reference to the key in the keyring with key_put(). With this fix, restoring pre-v6.9 behavior, the copy in the thread keyring is then promptly garbage collected, such that exactly one copy of the volume key remains. This single copy is correctly wiped from memory on "cryptsetup luksSuspend". Without this fix, the thread keyring and the volume key in it remains. This second copy is only freed on "luksClose". "luksSuspend" neither knows about this copy nor has any way to remove it, so the key remains recoverable from RAM after a suspend that is documented to have wiped it. This fix should not introduce new security problems, as the code is anyway gated by CAP_SYS_ADMIN. The device-mapper core, not the calling task, is the legitimate owner of this long-lived file.
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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.3 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Lsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 5.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.9 | 6.12.101 | d3eb8451d529 |
| 6.9 | 6.18.42 | 8ced1d242c34 |
| 6.9 | 7.1.5 | f00105be6a59 |
| 6.9 | 7.2 | 981ccd97f715 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | 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 bug is in open_table_device(), reached when CAP_SYS_ADMIN holders ioctl DM_TABLE_LOAD on /dev/mapper/control; table_load→populate_table→crypt_ctr→dm_get_device→bdev_file_open_by_dev pins caller creds. No network or physical-bus path reaches this code.
- AC:LAttack complexity, low
- On every dm-crypt table load using cryptsetup's standard :logon: thread-keyring key path, bdev_file_open_by_dev unconditionally pins current_cred() into the long-lived table-device file; the extra volume-key copy then survives luksSuspend until luksClose with no race or victim-dependent heap layout.
- PR:LPrivileges required, low
- ctl_ioctl requires capable(CAP_SYS_ADMIN) before dm commands; per kernel CNA guidance CAP_SYS_ADMIN obtainable in a user namespace maps to Low, and attackers routinely use namespace-level dm-crypt/LUKS administration on servers, containers, and encrypted workstations.
- UI:NUser interaction, none
- Exploitation does not require a victim to open untrusted files or mount attacker media; the latent leaked key is created by routine automated cryptsetup luksOpen/luksSuspend during boot and system suspend on LUKS deployments.
- S:UScope, unchanged
- The flaw only prevents wiping a dm-crypt volume key still held in a pinned thread keyring within the host kernel; it does not cross VM/hypervisor, IOMMU, or other separate security-authority boundaries.
- C:HConfidentiality impact, high
- luksSuspend is documented to remove all in-kernel copies of the LUKS volume key, but the pinned logon-key payload in the leaked thread keyring remains recoverable from RAM via forensic access until luksClose, exposing the full disk-encryption key.
- I:HIntegrity impact, high
- Recovery of the dm-crypt volume key grants an attacker unrestricted read and write access to the entire LUKS-protected block device, enabling undetected modification of all encrypted data the suspend operation was meant to keep inaccessible.
- A:LAvailability impact, low
- The pinned bdev_file keeps the caller's credentials and thread keyring (with logon key material) allocated for the dm device lifetime; this is a long-lived kernel memory retention/leak without crash, though not a service outage.