CVE-2026-45944 — linux / linux_kernel
In the Linux kernel, the following vulnerability has been resolved:
iommu/vt-d: Clear Present bit before tearing down context entry
When tearing down a context entry, the current implementation zeros the entire 128-bit entry using multiple 64-bit writes. This creates a window where the hardware can fetch a "torn" entry — where some fields are already zeroed while the 'Present' bit is still set — leading to unpredictable behavior or spurious faults.
While x86 provides strong write ordering, the compiler may reorder writes to the two 64-bit halves of the context entry. Even without compiler reordering, the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes.
Align with the "Guidance to Software for Invalidations" in the VT-d spec (Section 6.5.3.3) by implementing the recommended ownership handshake:
- Clear only the 'Present' (P) bit of the context entry first to signal the transition of ownership from hardware to software.
- Use dma_wmb() to ensure the cleared bit is visible to the IOMMU.
- Perform the required cache and context-cache invalidation to ensure hardware no longer has cached references to the entry.
- Fully zero out the entry only after the invalidation is complete.
Also, add a dma_wmb() to context_set_present() to ensure the entry is fully initialized before the 'Present' bit becomes visible.
| Software | From | Fixed in |
|---|---|---|
| linux / linux_kernel | 2.6.24 | 6.18.14 |
| linux / linux_kernel | 6.19 | 6.19.4 |
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A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
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Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
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