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CVE-2026-89573
dm array: reject an array block whose value size is not the caller's
Published 2026-09-11 (37 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-2026-89573 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
array_block_check() can only compare the header against itself, so a block with value_size 4 and max_entries 1018 is internally consistent and passes. dm-cache keeps two arrays -- mappings at 8 bytes and hints at 4 -- and the roots for both live in the superblock. Point the mappings root at a hint block and __load_mappings() walks it through an info whose value size is 8, so element_at() strides 8 bytes over 4-byte entries and reaches offset 8160 of a 4096-byte block. get_ablock() and __shadow_ablock() are the two places that hold the block and the caller at once. Reject there when the two value sizes disagree. Arrays only ever read their own blocks, so this fires on crafted metadata only.
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/persistent-data/dm-array.c
- What this is
- DEVICE-MAPPER (LVM)MAINTAINERS section matched on drivers/md/persistent-data/ · dm-devel@lists.linux.dev · Maintained
- Kernel module
- dm_persistent_data
Check it on the machine
grep -wE 'CONFIG_DM_PERSISTENT_DATA|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_persistent_dataPrints 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_DM_PERSISTENT_DATA, 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
- 2026-09-11 (37 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
- 0.13%, higher than 2.3% 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 |
|---|---|---|
| 3.9 | 5.10.270 | 35cd3b278448 |
| 3.9 | 5.15.221 | a8237cb8fa0a |
| 3.9 | 6.1.188 | a530a9a419a7 |
| 3.9 | 6.6.157 | 522fa26da24c |
| 3.9 | 6.12.109 | 7bf4b5cb42a4 |
| 3.9 | 6.18.50 | ac4a5eb8b002 |
| 3.9 | 7.2.4 | cb409b38b023 |
| 3.9 | 7.3 | 4538a287bdf5 |
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 bug is reached when device-mapper loads crafted dm-cache/dm-era array metadata through the local DM ioctl path (table load and resume) or LVM autoactivation of a cache/era target; it is not processed from network packets or a USB host/gadget driver.
- AC:LAttack complexity, low
- The attacker fully controls the on-disk superblock roots and array headers, so pointing the 8-byte mappings root at a valid 4-byte hint block makes __load_mappings() deterministically stride off the 4096-byte bufio buffer; no race or layout outside the attacker's control is required.
- PR:LPrivileges required, low
- Planting the metadata only requires write access to the cache/era backing store (loop file, removable disk, iSCSI/NBD, or a container/VM-exposed block device), not init-namespace CAP_SYS_ADMIN on /dev/mapper/control; user namespaces cannot pass capable(CAP_SYS_ADMIN), but an unprivileged writer of that store is enough.
- UI:NUser interaction, none
- Activation of a dm-cache/dm-era target is routine device management (udev/LVM autoactivation, boot, or reattachment of the metadata device) and does not require a separate victim to mount a filesystem or otherwise opt in once the crafted metadata is in place.
- S:UScope, unchanged
- The out-of-bounds access stays inside kernel dm-bufio metadata buffers and cache policy state in the same kernel security authority; it is not a VM escape, IOMMU bypass, or other cross-authority boundary.
- C:HConfidentiality impact, high
- element_at() multiplies the caller's value size by the on-disk nr_entries, so the cursor reads thousands of bytes past the 4K dm-bufio page (offset 8160 of a 4096-byte block), leaking adjacent kernel memory into mapping, hint, and bitset values.
- I:HIntegrity impact, high
- The type-confused walk treats attacker-controlled hint bytes as 8-byte mappings and can shadow/fill the wrong-sized block, corrupting cache policy and subsequent origin/cache writeback; this is kernel memory unsafety with an out-of-bounds/type-confused write primitive, so integrity is high.
- A:HAvailability impact, high
- Walking off the mapped 4K bufio page into unmapped or invalid memory oopses the kernel, and a mismatched on-disk nr_entries versus the caller's max_entries can hit BUG_ON() in fill_ablock()/trim_ablock() on resize.