CVE-2026-45945 (GCVE-0-2026-45945)

Vulnerability from cvelistv5 – Published: 2026-05-27 12:18 – Updated: 2026-08-05 12:28
VLAI
Title
iommu/vt-d: Fix race condition during PASID entry replacement
Summary
In the Linux kernel, the following vulnerability has been resolved: iommu/vt-d: Fix race condition during PASID entry replacement The Intel VT-d PASID table entry is 512 bits (64 bytes). When replacing an active PASID entry (e.g., during domain replacement), the current implementation calculates a new entry on the stack and copies it to the table using a single structure assignment. struct pasid_entry *pte, new_pte; pte = intel_pasid_get_entry(dev, pasid); pasid_pte_config_first_level(iommu, &new_pte, ...); *pte = new_pte; Because the hardware may fetch the 512-bit PASID entry in multiple 128-bit chunks, updating the entire entry while it is active (Present bit set) risks a "torn" read. In this scenario, the IOMMU hardware could observe an inconsistent state — partially new data and partially old data — leading to unpredictable behavior or spurious faults. Fix this by removing the unsafe "replace" helpers and following the "clear-then-update" flow, which ensures the Present bit is cleared and the required invalidation handshake is completed before the new configuration is applied.
Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 7543ee63e8113aa34b07df3b16b3b9d2c5f73939 , < 4718007870547e1efebbdd6745d9fce58f008fef (git)
Affected: 7543ee63e8113aa34b07df3b16b3b9d2c5f73939 , < 66a7aff480a82b8642b3991fed5fdc9780022157 (git)
Affected: 7543ee63e8113aa34b07df3b16b3b9d2c5f73939 , < c3b1edea3791fa91ab7032faa90355913ad9451b (git)
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Linux Linux Affected: 6.13
Unaffected: 0 , < 6.13 (semver)
Unaffected: 6.18.39 , ≤ 6.18.* (semver)
Unaffected: 6.19.4 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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            "drivers/iommu/intel/iommu.c",
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            "drivers/iommu/intel/pasid.h"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\niommu/vt-d: Fix race condition during PASID entry replacement\n\nThe Intel VT-d PASID table entry is 512 bits (64 bytes). When replacing\nan active PASID entry (e.g., during domain replacement), the current\nimplementation calculates a new entry on the stack and copies it to the\ntable using a single structure assignment.\n\n        struct pasid_entry *pte, new_pte;\n\n        pte = intel_pasid_get_entry(dev, pasid);\n        pasid_pte_config_first_level(iommu, \u0026new_pte, ...);\n        *pte = new_pte;\n\nBecause the hardware may fetch the 512-bit PASID entry in multiple\n128-bit chunks, updating the entire entry while it is active (Present\nbit set) risks a \"torn\" read. In this scenario, the IOMMU hardware\ncould observe an inconsistent state \u2014 partially new data and partially\nold data \u2014 leading to unpredictable behavior or spurious faults.\n\nFix this by removing the unsafe \"replace\" helpers and following the\n\"clear-then-update\" flow, which ensures the Present bit is cleared and\nthe required invalidation handshake is completed before the new\nconfiguration is applied."
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              "value": "AV:L - The vulnerable replace path is reached only through local IOMMUFD/VFIO ioctls (`/dev/iommu` device PASID domain replacement); there is no network or remote-peer path to this code.\nAC:L - Although it is a hardware/software race on the 128-bit-chunked entry fetch, the attacker controls both sides \u2014 driving continuous device DMA (forcing frequent entry fetches) while repeatedly issuing the replacement ioctl \u2014 so the torn-entry window is reliably reachable through repetition.\nPR:L - Triggering domain replacement requires IOMMUFD/VFIO access to an assigned device, which is gated by device-file permissions rather than an init-namespace root capability check; a confined VMM/user granted passthrough suffices.\nUI:N - The replacement and concurrent DMA are entirely attacker-driven; no action by another user is needed.\nS:C - The flaw is in the IOMMU DMA-isolation structure, and a torn PASID entry can let a device\u0027s DMA escape its assigned domain \u2014 an IOMMU/DMA boundary bypass that crosses the security authority of the affected component.\nC:H - A torn page-table-pointer field can cause the IOMMU to translate device DMA through stale/corrupt tables, allowing the device to read host or other-domain physical memory across the isolation boundary.\nI:H - The same mistranslation gives the device a write primitive into memory outside its domain, enabling corruption of host/other-domain memory.\nA:H - The commit explicitly notes the torn entry causes \"unpredictable behavior or spurious faults,\" which can manifest as IOMMU faults, device failures, or kernel crashes."
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    "dateReserved": "2026-05-13T15:03:33.088Z",
    "dateUpdated": "2026-08-05T12:28:52.094Z",
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-18T21:35:34+00:00",
      "cve": "CVE-2026-45945",
      "id": "CVE-2026-45945",
      "initial_release_date": "2026-05-27T00:00:00+00:00",
      "product_status:known_affected": "184",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: iommu/vt-d: Fix race condition during PASID entry replacement",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45945.json",
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      "current_release_date": "2026-08-06T01:18:51Z",
      "cve": "CVE-2026-45945",
      "id": "CVE-2026-45945",
      "initial_release_date": "2026-05-28T03:55:41Z",
      "product_status:known_not_affected": "293",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-45945",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-45945.json",
      "version": "5"
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}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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