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CVE-2026-64152
iommu: Handle unmap error when iommu_debug is enabled
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem drivers/iommu. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64152 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 | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Sashiko noticed a latent bug where the map error flow called iommu_unmap() which calls iommu_debug_unmap_begin()/iommu_debug_unmap_end() however since this is an error path the map flow never actually established the original iommu_debug_map() it will malfunction. Lift the unmap error handling into iommu_map_nosync() and reorder it so the trace_map()/iommu_debug_map() records the partial mapping and then immediately unmaps it. This avoid creating the unbalanced tracking and provides saner tracing instead of a unmap unmatched to any map.
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/iommu/iommu.c
- What this is
- IOMMU SUBSYSTEMMAINTAINERS section matched on drivers/iommu/ · iommu@lists.linux.dev · Maintained
Check it on the machine
grep -w CONFIG_IOMMU_API /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 builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_IOMMU_API
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
- 2026-07-19 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.14%, higher than 3.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/iommu
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 7.0 | 7.0.11 | 0cd028806efc |
| 7.0 | 7.1 | 0735c54804c7 |
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 vulnerable code is reached only through local kernel IOMMU APIs invoked from userspace ioctl paths such as IOMMUFD IOAS mapping (/dev/iommu) and VFIO DMA mapping (/dev/vfio/vfio), not from any network packet handler.
- AC:HAttack complexity, high
- Exploitation requires CONFIG_IOMMU_DEBUG_PAGEALLOC plus the iommu.debug_pagealloc=1 boot parameter (both admin-controlled debug options absent from production kernels) and a partial IOMMU map failure, conditions the attacker cannot establish unilaterally.
- PR:LPrivileges required, low
- Triggering iommu_map() requires only local userspace access to IOMMUFD or VFIO interfaces (e.g., /dev/vfio/vfio at mode 0666), which an unprivileged local user or cloud VM tenant with assigned passthrough devices can obtain without host root.
- UI:NUser interaction, none
- No victim interaction is required; the attacker triggers the bug directly through IOMMU map ioctl operations that fail partway through.
- S:CScope, changed
- The bug corrupts IOMMU page-tracking metadata used to enforce the DMA/IOMMU security boundary, and a VM tenant with VFIO passthrough can trigger it in the host kernel, crossing the guest-to-host security authority.
- C:HConfidentiality impact, high
- Unbalanced debug refcount decrements corrupt page_ext IOMMU tracking state, which can suppress detection of pages still mapped for DMA and thereby permit device reads of host physical memory that should be isolated.
- I:HIntegrity impact, high
- Corrupted IOMMU debug tracking is memory corruption in kernel metadata that can mask stale DMA mappings, enabling a device to write host memory across the IOMMU boundary; WARN_ON underflow paths also demonstrate uncontrolled kernel state corruption.
- A:HAvailability impact, high
- The bug triggers WARN_ON on atomic refcount underflow during unmap_begin/dec_page, which can cause kernel oops or panic (especially with panic_on_warn), constituting high availability impact.