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CVE-2026-89494
ocfs2: validate lengths in dlm_mig_lockres_handler
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem fs/ocfs2. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89494 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
A node receiving a DLM_MIG_LOCKRES message trusts several fields of the peer-supplied dlm_migratable_lockres without validation. num_locks and lockname_len are bounded only on the sending side, and the message is never checked to actually carry num_locks migratable_lock entries. As a result dlm_process_recovery_data() walks mres->ml[0..num_locks) past the kmalloc(data_len) copy of the message (an out-of-bounds read that ends in a BUG_ON panic), and dlm_init_lockres() copies lockname_len bytes into the fixed 32-byte o2dlm_lockname slab object (a heap out-of-bounds write). Both are reachable by any node in the domain. Validate these fields right after dlm_grab(), before anything uses them -- including the not-joined error path, which already prints mres->lockname with the unbounded lockname_len as a %.*s precision. Reject the message unless lockname_len <= DLM_LOCKID_NAME_MAX, num_locks <= DLM_MAX_MIGRATABLE_LOCKS (the bound the sender already asserts), and the payload is large enough to hold the claimed locks. Conforming recovery and migration messages are unaffected.
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.
fs/ocfs2/dlm/dlmrecovery.c
- What this is
- ORACLE CLUSTER FILESYSTEM 2 (OCFS2)MAINTAINERS section matched on fs/ocfs2/ · ocfs2-devel@lists.linux.dev · Supported
- Kernel module
- ocfs2_dlm
Check it on the machine
grep -wE 'CONFIG_OCFS2_FS|CONFIG_OCFS2_FS_O2CB' /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 ocfs2_dlmPrints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_OCFS2_FS, CONFIG_OCFS2_FS_O2CB
- 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
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.71%, higher than 52.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/ocfs2
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.16 | 5.10.270 | 4a5798253212 |
| 2.6.16 | 5.15.221 | dce05b17db86 |
| 2.6.16 | 6.1.188 | 0e999d56917f |
| 2.6.16 | 6.6.157 | 77686fa5bba1 |
| 2.6.16 | 6.12.109 | f33041906885 |
| 2.6.16 | 6.18.50 | 50c4cc9183e1 |
| 2.6.16 | 7.2.4 | a8facb1670b4 |
| 2.6.16 | 7.3 | b54e03d9b369 |
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:NAttack vector, network
- DLM_MIG_LOCKRES is received and dispatched by the ocfs2 o2net TCP cluster transport, so dlm_mig_lockres_handler() is reached through network protocol messages from a peer node.
- AC:LAttack complexity, low
- A cluster peer can send a crafted DLM_MIG_LOCKRES with attacker-chosen lockname_len and num_locks; the heap overflow and BUG_ON are deterministic and require no race or other condition outside the attacker's control.
- PR:NPrivileges required, none
- o2net gates peers by configured node IP, heartbeat, and the DLM domain key, with no user authentication or target-local privilege check before the handler runs, so exploitation needs no account on the victim.
- UI:NUser interaction, none
- Once the OCFS2/DLM domain is joined, exploitation is driven entirely by attacker-sent o2net messages and requires no victim user action such as mounting or opening a file.
- S:UScope, unchanged
- The heap corruption and resulting kernel impact remain within the same kernel and OCFS2 cluster-node security authority and do not cross a guest-to-host or IOMMU boundary.
- C:HConfidentiality impact, high
- Unchecked lockname_len and num_locks produce a heap out-of-bounds write of attacker-controlled bytes and an out-of-bounds read past the kmalloc message copy, which can disclose adjacent kernel memory.
- I:HIntegrity impact, high
- dlm_init_lockres() memcpy()s up to 255 attacker-controlled bytes into a 32-byte o2dlm_lockname slab object, a heap out-of-bounds write that can overwrite adjacent objects and hijack kernel control flow.
- A:HAvailability impact, high
- dlm_process_recovery_data() walks mres->ml[] past the allocated message and hits BUG_ON, and the heap overflow can oops or panic the receiving node.