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CVE-2026-64430
NTB: epf: Avoid calling pci_irq_vector() from hardirq context
Published 2026-07-25 (3 months ago) by the Linux kernel CNA. Subsystem drivers/ntb. Debian urgency: not yet assigned.
Debian does not build this code. The per-release build detail is under "Where it lives" below.
What to do, per Debian release
Debian's own status for CVE-2026-64430 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-4720-1 · 2026-08-05 · text | 6.1.180-1 | Update the kernel and reboot. DLA-4720-1 shipped the fix on 2026-08-05, in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.96-1 | Update the kernel and reboot. Fixed in 6.12.96-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ntb_epf_vec_isr() calls pci_irq_vector() in hardirq context to derive the vector number. pci_irq_vector() calls msi_get_virq() that takes a mutex and can therefore trigger "scheduling while atomic" splats: BUG: scheduling while atomic: kworker/u33:0/55/0x00010001 ... Call trace: ... schedule+0x38/0x110 schedule_preempt_disabled+0x28/0x50 __mutex_lock.constprop.0+0x848/0x908 __mutex_lock_slowpath+0x18/0x30 mutex_lock+0x4c/0x60 msi_domain_get_virq+0xe8/0x138 pci_irq_vector+0x2c/0x60 ntb_epf_vec_isr+0x28/0x120 [ntb_hw_epf] __handle_irq_event_percpu+0x70/0x3a8 handle_irq_event+0x48/0x100 handle_edge_irq+0x100/0x1c8 ... Cache the Linux IRQ number for vector 0 when vectors are allocated and use it as a base in the ISR. Running the ISR in a threaded IRQ handler would also avoid the problem, but that would be unnecessary here.
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/ntb/hw/epf/ntb_hw_epf.c
- What this is
- NTB DRIVER COREMAINTAINERS section matched on drivers/ntb/ · ntb@lists.linux.dev · Supported
- Kernel module
- none to look for. The file would have gone into ntb_hw_epf, and Debian does not compile it into that module, so finding ntb_hw_epf in lsmod would say nothing about this CVE.
Check it on the machine
grep -wE 'CONFIG_NTB|CONFIG_NTB_EPF' /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 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12n
- n
- not enabled on any flavour - this release does not build the code
- Build switches
- CONFIG_NTB, CONFIG_NTB_EPF
- 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
- 2026-07-25 (3 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.49%, higher than 40.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/ntb
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.12 | 5.15.212 | 33bba331a4a5 |
| 5.12 | 6.1.178 | aff271b12a1e |
| 5.12 | 6.6.145 | 1dba8444ac01 |
| 5.12 | 6.12.96 | 174a97f21bf9 |
| 5.12 | 6.18.39 | f71e8d987506 |
| 5.12 | 7.1.4 | 6350df503897 |
| 5.12 | 7.2 | 4dcddc1c794d |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | tracker |
| DLA-4723-1 | 2026-08-07 | bullseye 6.1.180-1~deb11u1 | tracker |
| DLA-4720-1 | 2026-08-05 | bookworm 6.1.180-1 | 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
- Routed traffic over the standard NTB Netdev interface causes the peer host to ring the victim's PCIe MSI/MSI-X doorbell, so an unauthenticated remote sender can reach the vulnerable interrupt handler.
- AC:LAttack complexity, low
- Every delivered doorbell enters the sleep-capable MSI lookup, and the attacker can repeatedly or concurrently trigger multiple allocated vectors to drive mutex contention.
- PR:NPrivileges required, none
- NTB Netdev traffic and peer doorbells have no victim-side authentication or capability check, so an unauthenticated network sender needs no privileges.
- UI:NUser interaction, none
- Once the NTB link is deployed, receiving traffic automatically invokes the hardirq handler without victim user action.
- S:UScope, unchanged
- The resulting failure affects the vulnerable host kernel itself and does not cross a VM, IOMMU, or other security-authority boundary.
- C:NConfidentiality impact, none
- The bug performs no out-of-bounds access or disclosure and provides no kernel-memory read primitive.
- I:NIntegrity impact, none
- The defect is an illegal sleep and mutex wait in hardirq context, with no memory corruption, arbitrary write, or data-modification primitive.
- A:HAvailability impact, high
- Mutex contention in hardirq context can cause scheduling-while-atomic failures, deadlock or hang, and a kernel panic on hardened panic-on-warning systems.