Critical severity · published Aug 15, 2026
CVE-2026-74439
iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry
9.3
CVSS
0.2%
EPSS
No
On KEV
Description
In the Linux kernel, the following vulnerability has been resolved:
iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry
device_pasid_table_teardown() zeroes the 128-bit scalable-mode context
entry with context_clear_entry() while the Present bit is still set. This
creates a window where the hardware can fetch a torn entry, with some
fields already zeroed while Present is still set, leading to unpredictable
behavior or spurious faults. The context-cache invalidation is issued only
after the entry has been zeroed, and intel_pasid_free_table() then frees
the PASID directory pages, so the IOMMU can keep walking a stale Present=1
entry that points at freed memory.
While x86 provides strong write ordering, the compiler may reorder the two
64-bit writes to the entry, and the hardware fetch is not guaranteed to be
atomic with respect to multiple CPU writes.
Commit c1e4f1dccbe9d ("iommu/vt-d: Clear Present bit before tearing down
context entry") fixed this exact pattern in domain_context_clear_one() and
the copied-context path, but device_pasid_table_teardown() was not
converted.
Align it with the "Guidance to Software for Invalidations" in the VT-d
spec, Section 6.5.3.3, using the same ownership handshake as the sibling
fix: clear only the Present bit, flush it to the IOMMU, perform the
context-cache invalidation, and only then zero the rest of the entry.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 9% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LI
Linux · Linux
81e921fd321614c2ad8ac333b041aae1da7a1c6d before e9e83bcfe37dc719182500dd823c03ab57d934f0; 81e921fd321614c2ad8ac333b041aae1da7a1c6d before 588718101e8449605f1c7e858fecb7cfa701cdab; 81e921fd321614c2ad8ac333b041aae1da7a1c6d before 7fd4077dc92b91b1b844333c0a06bb9e286db10a; 81e921fd321614c2ad8ac333b041aae1da7a1c6d before f46452c3df7a8d8a5addc0926e76ef19ea7da0a0; 333fe86968482ca701c609af590003bcea450e8f; 6.8.2 before 6.9; +1 more · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-74439
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-74439
git.kernel.org
https://git.kernel.org/stable/c/588718101e8449605f1c7e858fecb7cfa701cdab
git.kernel.org
https://git.kernel.org/stable/c/7fd4077dc92b91b1b844333c0a06bb9e286db10a
git.kernel.org
https://git.kernel.org/stable/c/e9e83bcfe37dc719182500dd823c03ab57d934f0
git.kernel.org
https://git.kernel.org/stable/c/f46452c3df7a8d8a5addc0926e76ef19ea7da0a0
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