CVE-2026-90243: Linux Vulnerability (CVSS 8.1)

Description

In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Clear Present bit before tearing down copied context entry copied_context_tear_down() zeroes the 128-bit context entry with context_clear_entry() while the Present bit is still set, and only then issues the context-cache and IOTLB invalidations. This leaves a window in which hardware can fetch a torn entry, with some fields already zeroed while Present is still set, leading to unpredictable behaviour or spurious faults. While x86 provides strong write ordering, the compiler may reorder the writes to the two 64-bit halves of the entry, and the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes. There is no cacheline flush before the invalidation either, so on an IOMMU without coherent access to the context table the zeroed entry may not be visible to hardware at the point the invalidation is submitted. Apply the same ownership handshake described in the VT-d spec, Section 6.5.3.3 ("Guidance to Software for Invalidations"): clear only the Present bit, flush it out to the IOMMU, perform the invalidations, and only then zero the remainder of the entry.

Metrics

CVSS 3.1

8.1/10

CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= c7191984e5aade540f1a3845a116537c89572655, < 97750a8dce79c1a9b2b2d2a020b61b800141996c; >= c7191984e5aade540f1a3845a116537c89572655, < 3c88cfedc7768b1ae2dc7ddc71547ae9a1aaff7d; >= c7191984e5aade540f1a3845a116537c89572655, < 6b822d18c33af9d1e16a8e5e6aa6e656987b09de; >= c7191984e5aade540f1a3845a116537c89572655, < f532c57985b1a7d6b7e37e05506b46d413e5cca4
Linux	Linux	6.12

References

Timeline

Published: Sep 17, 2026
Last Modified: Sep 18, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-90243?

In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Clear Present bit before tearing down copied context entry copied_context_tear_down() zeroes the 128-bit context entry with context_clear_entry() while the Present bit is still set, and only then issues the context-cache and IOTLB invalidations. This leaves a window in which hardware can fetch a torn entry, with some fields already zeroed while Present is still set, leading to unpredictable behaviour or spurious faults. While x86 provides strong write ordering, the compiler may reorder the writes to the two 64-bit halves of the entry, and the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes. There is no cacheline flush before the invalidation either, so on an IOMMU without coherent access to the context table the zeroed entry may not be visible to hardware at the point the invalidation is submitted. Apply the same ownership handshake described in the VT-d spec, Section 6.5.3.3 ("Guidance to Software for Invalidations"): clear only the Present bit, flush it out to the IOMMU, perform the invalidations, and only then zero the remainder of the entry.

How severe is CVE-2026-90243?

CVE-2026-90243 has a CVSS score of 8.1/10 (HIGH severity).

How do I fix CVE-2026-90243?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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