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CVE-2026-43125
dlm: validate length in dlm_search_rsb_tree
Published 2026-05-06 (5 months ago) by the Linux kernel CNA. Subsystem fs/dlm. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-43125 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 | fixed | 6.12.85-1 | Update the kernel and reboot. Fixed in 6.12.85-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 6.19.6-1 | Update the kernel and reboot. Fixed in 6.19.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.19.6-1 | Update the kernel and reboot. Fixed in 6.19.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The len parameter in dlm_dump_rsb_name() is not validated and comes from network messages. When it exceeds DLM_RESNAME_MAXLEN, it can cause out-of-bounds write in dlm_search_rsb_tree(). Add length validation to prevent potential buffer overflow.
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/dlm/lock.c
- What this is
- DISTRIBUTED LOCK MANAGER (DLM)MAINTAINERS section matched on fs/dlm/ · gfs2@lists.linux.dev · Supported
- Kernel module
- dlm
Check it on the machine
grep -w CONFIG_DLM /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 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 switch
- CONFIG_DLM
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
- 2026-05-06 (5 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
- 0.43%, higher than 35.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/dlm
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.4 | 6.12.75 | 67288113c5e6 |
| 3.4 | 6.18.16 | 082083c9fbd9 |
| 3.4 | 6.19.6 | 5f053a2e7209 |
| 3.4 | 7.0 | 080e5563f878 |
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
- The vulnerable path is reached by DLM recovery messages received over the kernel DLM TCP/SCTP lowcomms transport from a remote cluster peer. Although the peer address must match configured cluster membership, the bug is triggered by network protocol data delivered to the target kernel.
- AC:LAttack complexity, low
- A remote peer that can send DLM recovery traffic controls the malformed RCOM_LOOKUP packet, including the special debug rc_id and oversized length/name payload. The recovery-state gate is a normal DLM condition that a participating peer can plausibly induce or target, so exploitation does not depend on conditions outside attacker control.
- PR:NPrivileges required, none
- The vulnerable receive path does not require credentials or privileges on the target system before parsing the packet. Cluster peer/source-address admission is not a privilege on the vulnerable host, and there is no DLM authentication check before the oversized name reaches the copy.
- UI:NUser interaction, none
- No victim user action is required once the target DLM lockspace is active and receiving cluster traffic. The attacker sends the malformed recovery message directly.
- S:UScope, unchanged
- The impact is compromise or crash of the target kernel within the same security authority. This is not a VM escape, IOMMU bypass, or other cross-scope boundary.
- C:HConfidentiality impact, high
- The bug is a network-controlled stack buffer overflow in the kernel, copying up to socket-buffer-sized attacker data into a 64-byte resource-name key. Such memory corruption is defensibly exploitable for kernel information disclosure as part of code execution or memory disclosure primitives.
- I:HIntegrity impact, high
- The oversized memcpy can corrupt the kernel stack, including control data, from attacker-controlled network bytes. This supports arbitrary kernel memory modification or code execution in the highest reasonable scenario.
- A:HAvailability impact, high
- Even without reliable code execution, the stack overflow can corrupt kernel control state and readily crash or panic the system. The malformed packet can be sent remotely whenever the vulnerable DLM receive path is reachable.