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CVE-2026-74629
net/dibs: Correct freeing of dmb_clientid_arr
Published 2026-08-22 (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-2026-74629 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
A dibs device interrupt handler can be active after dibs_dev_del() and may still access dmb_clientid_arr. (UAF) In case of a failure in dibs_dev_add() being called by dibs_lo_dev_probe() dmb_clientid_arr is freed twice (double free). Free dmb_clientid_arr in dibs_dev_release() after last reference is gone. Note that allocating in dibs_dev_add() instead of dibs_dev_alloc() is ok for now, because no dmbs can be registered before dibs_dev_add().
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
drivers/dibs/dibs_main.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
- 2026-08-22 (2 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.38%, higher than 29.9% 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 |
|---|---|---|
| 6.18 | 6.18.45 | ece6426b6124 |
| 6.18 | 7.1.9 | 7a1df20a8d2c |
| 6.18 | 7.2 | 9e6869be4906 |
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:AAttack vector, adjacent network
- The UAF is hit when an ISM interrupt handler reads dmb_clientid_arr during SMC-D data transfer from a co-located peer on the same IBM Z CPC/HiperSockets domain; this is an adjacent-network attack surface, not arbitrary Internet reachability.
- AC:LAttack complexity, low
- An attacker controls the IRQ side by sustaining SMC-D transfers that keep firing ism_handle_irq while device teardown runs; no rare memory layout or victim-specific state beyond concurrent traffic during hot-unplug/module removal is required.
- PR:NPrivileges required, none
- Exploitation requires only an established SMC-D peer sending data to the victim; no Linux capabilities, root, or user-namespace privileges on the victim host are needed to drive the interrupt path that accesses the freed array.
- UI:NUser interaction, none
- No victim user action is required; the bug is triggered by remote SMC-D traffic coinciding with kernel driver teardown, not by opening files, mounting filesystems, or other interactive steps.
- S:UScope, unchanged
- Successful exploitation corrupts kernel heap memory and enables privilege escalation within the same kernel security domain; it does not by itself cross a VM/hypervisor or IOMMU boundary to another authority.
- C:HConfidentiality impact, high
- The use-after-free of dmb_clientid_arr in ism_handle_irq permits out-of-bounds or attacker-influenced kernel heap reads that can disclose sensitive memory, including pointers usable in further exploitation.
- I:HIntegrity impact, high
- UAF on a heap-allocated client-ID lookup table in IRQ context can be turned into arbitrary kernel memory writes and control-flow hijacking via heap grooming and reuse of the freed allocation.
- A:HAvailability impact, high
- Concurrent access to freed dmb_clientid_arr during interrupt handling can cause kernel oops/panic or wedged SMC-D processing, producing complete loss of availability on affected IBM Z systems.