CVE-2026-64034 (GCVE-0-2026-64034)
Vulnerability from cvelistv5
Published
2026-07-19 15:39
Modified
2026-08-05 12:38
Severity ?
9.3 (Critical) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer In mana_hwc_rx_event_handler(), resp->response.hwc_msg_id is read from DMA-coherent memory and bounds-checked, then mana_hwc_handle_resp() re-reads the same field from the same DMA buffer for test_bit() and pointer arithmetic. DMA-coherent memory is mapped uncacheable on x86 and is shared, unencrypted, in Confidential VMs (SEV-SNP/TDX), so each load goes directly to host-visible memory. A H/W can modify the value between the check and the use, bypassing the bounds validation. Fix this by reading hwc_msg_id exactly once using READ_ONCE() into a stack-local variable in mana_hwc_rx_event_handler(), and passing the validated value as a parameter to mana_hwc_handle_resp().
References
Impacted products
Vendor Product Version
Linux Linux Version: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f
Version: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f
Version: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f
Version: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f
Version: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f
Version: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f
Version: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f
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{
  "containers": {
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          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/ethernet/microsoft/mana/hw_channel.c"
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          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "version": "5.15.209",
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            {
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              "status": "unaffected",
              "version": "6.1.175",
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            {
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              "version": "6.6.142",
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              "status": "unaffected",
              "version": "6.12.92",
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            },
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.34",
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            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.11",
              "versionType": "semver"
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            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "versionEndExcluding": "5.15.209",
                  "versionStartIncluding": "5.13",
                  "vulnerable": true
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                {
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer\n\nIn mana_hwc_rx_event_handler(), resp-\u003eresponse.hwc_msg_id is read from\nDMA-coherent memory and bounds-checked, then mana_hwc_handle_resp()\nre-reads the same field from the same DMA buffer for test_bit() and\npointer arithmetic.\n\nDMA-coherent memory is mapped uncacheable on x86 and is shared,\nunencrypted, in Confidential VMs (SEV-SNP/TDX), so each load goes\ndirectly to host-visible memory. A H/W can modify the value\nbetween the check and the use, bypassing the bounds validation.\n\nFix this by reading hwc_msg_id exactly once using READ_ONCE() into a\nstack-local variable in mana_hwc_rx_event_handler(), and passing the\nvalidated value as a parameter to mana_hwc_handle_resp()."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.3,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires a malicious hypervisor or host that can modify MANA HWC DMA-coherent response buffers between guest kernel loads; it is not reachable by sending network packets to the guest\u0027s data path.\nAC:L - The attacker controlling the hypervisor fully controls DMA buffer contents and can reliably flip hwc_msg_id between the validation read and the use in mana_hwc_handle_resp() on uncacheable coherent memory.\nPR:N - The attacking hypervisor needs no guest OS credentials or capabilities; exploitation targets the guest kernel through the virtual device DMA path while the MANA driver is active.\nUI:N - No victim user action is required beyond normal Azure VM operation with the MANA driver loaded and HWC receive buffers posted.\nS:C - The vulnerability crosses the VM/DMA security boundary by allowing a hostile hypervisor to corrupt guest kernel memory that the confidential-guest threat model assumes is protected from host tampering.\nC:H - Out-of-bounds indexing via bypassed hwc_msg_id validation enables reading adjacent kernel heap objects through misdirected caller_ctx access and test_bit() on the inflight bitmap.\nI:H - Host-controlled response data is copied with memcpy() to an out-of-bounds output_buf pointer, enabling arbitrary kernel memory corruption and potential control-flow hijacking.\nA:H - Out-of-bounds caller_ctx access and corrupted completion signaling can cause kernel oops, panic, or hang during HWC response handling."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:38:28.529Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a201c66edf2ebc6cfdc3813a889ba20fecebfae3"
        },
        {
          "url": "https://git.kernel.org/stable/c/70ad2dff8d052a85dfef15715b531f38a29108cf"
        },
        {
          "url": "https://git.kernel.org/stable/c/566f42fb67a7ebfed6650e407e5b72e6b3e83bf7"
        },
        {
          "url": "https://git.kernel.org/stable/c/6180a06bbc99fd9114b8db4be6c4d46e40f046ef"
        },
        {
          "url": "https://git.kernel.org/stable/c/09ec063d87c2dd3fa6f3561361a017bd882e9f37"
        },
        {
          "url": "https://git.kernel.org/stable/c/3c4db56ccd13dd020fbf43afabaee74a40ec75e4"
        },
        {
          "url": "https://git.kernel.org/stable/c/35f0f0a2536a4d604b4dbad92c85c4a8fdebb870"
        }
      ],
      "title": "net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64034",
    "datePublished": "2026-07-19T15:39:23.470Z",
    "dateReserved": "2026-07-19T07:54:57.028Z",
    "dateUpdated": "2026-08-05T12:38:28.529Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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