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CVE-2026-89574
dm array: validate array block headers on read
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-2026-89574 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| 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() validates blocknr and csum and nothing else, while node_check(), next to it, has bounded the structural fields since both were written. dm_array_cursor_next() takes its loop bound from the on-disk nr_entries and element_at() is unguarded pointer arithmetic, so a count larger than the block holds keeps the cursor in one block while the index grows past it and the read walks off the dm-bufio buffer -- dm_cache_load_mappings() drives it once per cache block at activation. Check the header against itself: reject a zero value_size, require max_entries to equal calc_max_entries() for that value_size and block size, and require nr_entries to fit. Equality rather than an upper bound, since a count below the real capacity trips BUG_ON() in fill_ablock() and trim_ablock(). Metadata dm-array writes satisfies all three.
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
- 0.17%, higher than 5.7% 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 | 6.12.109 | 67adda7ed5da |
| 3.9 | 6.18.50 | b33f76d33aae |
| 3.9 | 7.2.4 | 9808ddffb4bc |
| 3.9 | 7.3 | 296578772308 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| 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 the kernel reads attacker-crafted dm-array metadata from a local block device during device-mapper activation (dm-cache dm_cache_load_mappings, dm-clone bitset load, or dm-era array resize), not via a network protocol.
- AC:LAttack complexity, low
- The attacker fully controls the on-disk array-block header (nr_entries, max_entries, value_size) and can compute a matching checksum, so activation deterministically walks off the dm-bufio buffer; there is no race or attacker-uncontrollable memory layout.
- PR:LPrivileges required, low
- Device-mapper ioctls require init-namespace CAP_SYS_ADMIN and are not reachable via user namespaces, but the malformed data is on-disk metadata, so the attacker only needs write access to the backing store (loop file, VM/container disk, iSCSI/NBD LUN) that a dm-cache/dm-era/dm-clone stack is built on.
- UI:NUser interaction, none
- Once corrupt metadata is on the backing store, LVM/udev autoactivation, boot, or reattachment of the volume loads mappings without a separate victim action such as mounting a filesystem or opening a file.
- S:UScope, unchanged
- The out-of-bounds access is confined to kernel dm-bufio metadata buffers on the same host; this is ordinary kernel memory corruption, not a VM escape, IOMMU bypass, or sandbox boundary crossing.
- C:HConfidentiality impact, high
- dm_array_cursor_next() takes its loop bound from on-disk nr_entries while element_at() is unguarded pointer arithmetic, so a too-large count keeps the cursor in one block and reads past the dm-bufio data buffer (typically a 4K slab/page) for every cache block at activation, an unbounded kernel out-of-bounds read.
- I:HIntegrity impact, high
- Unchecked headers let fill_ablock()/trim_ablock() hit BUG_ON on resize, and out-of-bounds mapping, hint, and bitset values from adjacent kernel memory are installed into the cache policy and then used for origin/cache I/O, giving a memory-corruption integrity primitive.
- A:HAvailability impact, high
- Walking off the dm-bufio buffer causes a kernel oops or KASAN panic, and an undersized on-disk max_entries hits BUG_ON in fill_ablock() and trim_ablock() during array resize at activation.