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CVE-2026-53309
ocfs2/dlm: fix off-by-one in dlm_match_regions() region comparison
Published 2026-06-26 (4 months 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-2026-53309 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-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The local-vs-remote region comparison loop uses '<=' instead of '<', causing it to read one entry past the valid range of qr_regions. The other loops in the same function correctly use '<'. Fix the loop condition to use '<' for consistency and correctness.
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/dlmdomain.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, sidMnot 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
- 2026-06-26 (4 months 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
- 0.40%, higher than 32.6% 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 |
|---|---|---|
| 2.6.37 | 5.10.258 | 760ab35040ac |
| 2.6.37 | 5.15.209 | c60a2710b738 |
| 2.6.37 | 6.1.175 | 2a0673836f01 |
| 2.6.37 | 6.6.141 | 819d8ebad320 |
| 2.6.37 | 6.12.91 | d5403ae28085 |
| 2.6.37 | 6.18.33 | 1fb7f356547d |
| 2.6.37 | 7.0.10 | 426cd8eedac8 |
| 2.6.37 | 7.1 | 01b61e8dda9b |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | tracker |
| DLA-4664-1 | 2026-07-03 | bullseye 5.10.259-1 | 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_QUERY_REGION is received and dispatched by the ocfs2 o2net TCP cluster transport, so the vulnerable comparison is reached through network messages from a peer node.
- AC:LAttack complexity, low
- A peer that can reach the OCFS2 cluster transport can deterministically drive the join sequence and send a crafted region list; the off-by-one comparison is not a race and needs no unusual timing.
- PR:NPrivileges required, none
- The receive path does not require credentials or a local account on the target; it relies on cluster node/IP/heartbeat state rather than authenticated target privileges.
- UI:NUser interaction, none
- Once the OCFS2/DLM cluster service is running, exploitation is driven entirely by network protocol messages and requires no victim user action.
- S:UScope, unchanged
- The vulnerable component and resulting kernel/cluster filesystem effects remain within the same kernel and OCFS2 cluster security authority.
- C:HConfidentiality impact, high
- The bug is an out-of-bounds read of a region-sized entry beyond the valid qr_regions range, driven by attacker-supplied network state; under the required kernel scoring guidance, non-trivial out-of-bounds reads are treated as high confidentiality impact.
- I:HIntegrity impact, high
- The off-by-one can let a joining node pass heartbeat-region validation with an inconsistent region set, undermining DLM cluster membership safety and enabling severe shared-filesystem integrity corruption in a plausible OCFS2 deployment.
- A:HAvailability impact, high
- Accepting inconsistent heartbeat regions can lead to cluster miscoordination, fencing, hangs, or filesystem disruption, and the malformed query can be sent without user interaction once the join path is reachable.