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CVE-2026-72018
dibs: loopback: validate offset and size in move_data()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem drivers/dibs. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72018 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The loopback move_data() performs a memcpy into the registered DMB without checking whether offset + size exceeds the DMB length. Unlike real ISM hardware, which enforces memory region bounds natively, the software loopback has no such protection. A peer-supplied out-of-bounds offset or oversized write would result in an OOB write past the allocated kernel buffer. Add an explicit bounds check before the memcpy to reject such requests with -EINVAL.
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/dibs/dibs_loopback.c
- What this is
- DIBS (DIRECT INTERNAL BUFFER SHARING)MAINTAINERS section matched on drivers/dibs/ · netdev@vger.kernel.org · Supported
Check it on the machine
grep -wE 'CONFIG_DIBS|CONFIG_DIBS_LO' /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.
Show whether Debian builds this, per release
Debian does not build this code in 2 releases. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidn
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switches
- CONFIG_DIBS, CONFIG_DIBS_LO
- 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
- 2026-08-15 (2 months 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 6.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/dibs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.10 | 6.12.97 | ee188a6b264b |
| 6.10 | 6.18.40 | b2f426a9a228 |
| 6.10 | 7.1.5 | 94fe0ab01b48 |
| 6.10 | 7.2 | 78237e3c0720 |
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 flaw is only reachable via loopback-ISM (intra-OS DIBS), which requires matching local GID and shared kernel; exploitation is through AF_SMC sendmsg after SMC-D handshake, not remote packet handling on a network-facing stack path.
- AC:LAttack complexity, low
- A malicious SMC-D peer can supply crafted CLC dmbe_idx/dmbe_size values and send patterns that drive move_data() with attacker-controlled offset and size; no race or uncontrollable memory layout is required once loopback-ISM is active.
- PR:LPrivileges required, low
- Exploitation requires only an unprivileged local account able to open AF_SMC sockets and complete an SMC-D loopback handshake (no CAP_NET_ADMIN or root); the SMC CLC path performs no authentication beyond standard socket access controls.
- UI:NUser interaction, none
- No victim user action is needed when a malicious peer initiates an inbound SMC-D connection to a listening service; the attacker can trigger the OOB write by sending SMC-D data after handshake completion.
- S:UScope, unchanged
- The OOB write corrupts kernel heap memory within the same kernel security authority; successful exploitation yields local privilege escalation, not cross-VM, container-boundary, or IOMMU bypass scope change.
- C:HConfidentiality impact, high
- An out-of-bounds kernel heap write past the folio-allocated DMB buffer can corrupt adjacent kernel objects and be leveraged for arbitrary kernel memory disclosure, not merely a bounded leak or pure crash.
- I:HIntegrity impact, high
- The unchecked memcpy() allows controlled out-of-bounds writes beyond the registered DMB allocation, enabling heap corruption and potential arbitrary kernel code execution or control-flow hijacking.
- A:HAvailability impact, high
- Writing past the allocated DMB folio can immediately corrupt critical kernel structures and cause kernel oops, panic, or hang; heap corruption from the OOB write itself constitutes high availability impact.