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CVE-2026-90240
iommu/vt-d: Flush context cache with correct SID when tearing down aliases
Published 2026-09-17 (31 days ago) by the Linux kernel CNA. Subsystem drivers/iommu. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-90240 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 | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
domain_context_clear_one() and device_pasid_table_teardown() are both invoked once per DMA alias of a device. Each function locates the context entry using the bus/devfn pair provided by the pci_for_each_dma_alias() callback, then calls intel_context_flush_no_pasid(), which constructs a device-selective context-cache invalidation from info->bus and info->devfn (that is, always the requester ID of the device itself). As a result, for every alias other than the device’s own RID, the context entry that was just cleared in memory is never invalidated in the context cache. Hardware may continue using that stale cached entry. In the scalable-mode teardown path, intel_pasid_free_table() can then free the PASID directory still referenced by that stale entry, allowing the IOMMU to walk freed memory. Fix this by passing the source ID of the entry being torn down to intel_context_flush_no_pasid(), instead of deriving it from @info.
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/intel/iommu.c
drivers/iommu/intel/iommu.h
drivers/iommu/intel/pasid.c
- What this is
- INTEL IOMMU (VT-d)MAINTAINERS section matched on drivers/iommu/intel/ · iommu@lists.linux.dev · Supported
Check it on the machine
grep -w CONFIG_INTEL_IOMMU /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, 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.
- bookwormYnot built on arm64/arm64, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
- trixieYnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidYnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- Y
- built in where it is built at all; some flavours do not build it
- Build switch
- CONFIG_INTEL_IOMMU
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
- 2026-09-17 (31 days ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 6.3% 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 |
|---|---|---|
| 6.11 | 6.18.52 | a803141597d6 |
| 6.11 | 7.2.6 | 5baddf100b3b |
| 6.11 | 7.3 | c54e4ae971b9 |
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
- domain_context_clear_one() and device_pasid_table_teardown() run from local VFIO_DEVICE_DETACH_IOMMUFD_PT/ATTACH_IOMMUFD_PT (vfio_df_ioctl_detach_pt → iommufd_device_detach → blocking_domain_attach_dev → device_block_translation) and from intel_iommu_release_device on PCI removal. The bug is intel_context_flush_no_pasid() using the wrong SID, not bytes from a remote protocol.
- AC:LAttack complexity, low
- For every pci_for_each_dma_alias() RID other than info->bus/info->devfn, intel_context_flush_no_pasid() issues DMA_CCMD_DEVICE_INVL with the device's own RID, so the alias context-cache entry is never invalidated. A VFIO user who owns a dma_alias_mask or PCI-bridge-aliased device then DMAs with that alias SID; there is no uncontrolled race.
- PR:LPrivileges required, low
- vfio_device_fops_unl_ioctl handles VFIO_DEVICE_DETACH_IOMMUFD_PT with no capable() check; vfio_group_fops_open requires CAP_SYS_RAWIO only for VFIO_NO_IOMMU groups. A tenant VMM with a passed-through aliased PCI device (device-file access, not init-namespace root) can detach while keeping DMA active.
- UI:NUser interaction, none
- The attacker issues VFIO_DEVICE_DETACH_IOMMUFD_PT or closes the vfio device fd themselves, then continues DMA using the unflushed alias RID. No separate victim action such as mounting a filesystem is required.
- S:CScope, changed
- After the missed alias-SID flush, hardware keeps a Present context for that RID while intel_pasid_free_table() (scalable mode) or domain teardown (legacy domain_context_clear_one) frees the PASID directory or page tables. The IOMMU then walks those freed translation structures for device DMA, crossing the VT-d DMA isolation boundary.
- C:HConfidentiality impact, high
- A stale cached context for the alias SID still points at the PASID directory that intel_pasid_free_table() just freed, or at second-level page tables already torn down. Device DMA with that RID is translated through attacker-influencable freed pages, reading host memory outside the assigned domain.
- I:HIntegrity impact, high
- The same leftover cached page-table or PASID-directory pointer for the unflushed alias SID lets the device DMA-write host memory that software has already freed or reassigned, giving an arbitrary cross-domain write primitive.
- A:HAvailability impact, high
- IOMMU walks of the freed PASID directory or page tables via the stale alias-SID context cause DMAR faults, translation failures, and host oops/panic; the commit documents hardware continuing to use that cached entry after teardown.