Vulnerability-Lookup

GHSA-R5HJ-4CHX-57CX

Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-07-20 15:31

Details

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().

Severity

9.3 (Critical)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64034"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-19T16:17:43Z",
    "severity": "CRITICAL"
  },
  "details": "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().",
  "id": "GHSA-r5hj-4chx-57cx",
  "modified": "2026-07-20T15:31:56Z",
  "published": "2026-07-19T18:31:50Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64034"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/09ec063d87c2dd3fa6f3561361a017bd882e9f37"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/35f0f0a2536a4d604b4dbad92c85c4a8fdebb870"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3c4db56ccd13dd020fbf43afabaee74a40ec75e4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/566f42fb67a7ebfed6650e407e5b72e6b3e83bf7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6180a06bbc99fd9114b8db4be6c4d46e40f046ef"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/70ad2dff8d052a85dfef15715b531f38a29108cf"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a201c66edf2ebc6cfdc3813a889ba20fecebfae3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-64034 (GCVE-0-2026-64034)

Vulnerability from cvelistv5 – Published: 2026-07-19 15:39 – Updated: 2026-08-05 12:38

Title

net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer

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().

Severity

9.3 (Critical)


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

Assigner

Linux mitre root

References

7 references

URL	Tags
https://git.kernel.org/stable/c/a201c66edf2ebc6cf…
https://git.kernel.org/stable/c/70ad2dff8d052a85d…
https://git.kernel.org/stable/c/566f42fb67a7ebfed…
https://git.kernel.org/stable/c/6180a06bbc99fd911…
https://git.kernel.org/stable/c/09ec063d87c2dd3fa…
https://git.kernel.org/stable/c/3c4db56ccd13dd020…
https://git.kernel.org/stable/c/35f0f0a2536a4d604…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f , < a201c66edf2ebc6cfdc3813a889ba20fecebfae3 (git) Affected: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f , < 70ad2dff8d052a85dfef15715b531f38a29108cf (git) Affected: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f , < 566f42fb67a7ebfed6650e407e5b72e6b3e83bf7 (git) Affected: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f , < 6180a06bbc99fd9114b8db4be6c4d46e40f046ef (git) Affected: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f , < 09ec063d87c2dd3fa6f3561361a017bd882e9f37 (git) Affected: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f , < 3c4db56ccd13dd020fbf43afabaee74a40ec75e4 (git) Affected: ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f , < 35f0f0a2536a4d604b4dbad92c85c4a8fdebb870 (git)
Linux	Linux	Affected: 5.13 Unaffected: 0 , < 5.13 (semver) Unaffected: 5.15.209 , ≤ 5.15.* (semver) Unaffected: 6.1.175 , ≤ 6.1.* (semver) Unaffected: 6.6.142 , ≤ 6.6.* (semver) Unaffected: 6.12.92 , ≤ 6.12.* (semver) Unaffected: 6.18.34 , ≤ 6.18.* (semver) Unaffected: 7.0.11 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/ethernet/microsoft/mana/hw_channel.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "versions": [
            {
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              "status": "affected",
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              "versionType": "git"
            },
            {
              "lessThan": "70ad2dff8d052a85dfef15715b531f38a29108cf",
              "status": "affected",
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              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f",
              "versionType": "git"
            },
            {
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              "versionType": "git"
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            {
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              "status": "affected",
              "version": "ca9c54d2d6a5ab2430c4eda364c77125d62e5e0f",
              "versionType": "git"
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          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.13"
            },
            {
              "lessThan": "5.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
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              "status": "unaffected",
              "version": "5.15.209",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.1.175",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.142",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.92",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.34",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
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          "nodes": [
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      ],
      "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()."
        }
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            "baseSeverity": "CRITICAL",
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              "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."
            }
          ]
        }
      ],
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        "dateUpdated": "2026-08-05T12:38:28.529Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        {
          "url": "https://git.kernel.org/stable/c/35f0f0a2536a4d604b4dbad92c85c4a8fdebb870"
        }
      ],
      "title": "net: mana: Fix TOCTOU double-fetch of hwc_msg_id from DMA buffer",
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        "engine": "bippy-1.2.0"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64034",
    "datePublished": "2026-07-19T15:39:23.470Z",
    "dateReserved": "2026-07-19T07:54:57.028Z",
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    "state": "PUBLISHED"
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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GHSA-R5HJ-4CHX-57CX

CVE-2026-64034 (GCVE-0-2026-64034)

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