CVE-2026-52959 (GCVE-0-2026-52959)
Vulnerability from cvelistv5
Published
2026-06-24 16:28
Modified
2026-08-05 12:32
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: virt: sev-guest: Do not use host-controlled page order in cleanup path When issuing an extended guest request (SVM_VMGEXIT_EXT_GUEST_REQUEST), get_ext_report() allocates a buffer to retrieve a certificate blob from the host, keeping track of its size in report_req->certs_len. However, the host may return SNP_GUEST_VMM_ERR_INVALID_LEN, indicating an invalid buffer size, as well as the expected length of such buffer. get_ext_report() subsequently updates report_req->certs_len with the host-controlled value, and cleans up the buffer by computing a page order from such value. This is incorrect, as the host-provided length may not match the page order of the original allocation, potentially resulting in corruption in the page allocator. Fix this by using alloc_pages_exact() instead, and reusing @npages to compute the size passed to free_pages_exact(). For consistency, also use @npages to compute the size when allocating the pages, even though this last change has no functional effect.
References
Impacted products
Vendor Product Version
Linux Linux Version: 3e385c0d6ce88ac9916dcf84267bd5855d830748
Version: 3e385c0d6ce88ac9916dcf84267bd5855d830748
Version: 3e385c0d6ce88ac9916dcf84267bd5855d830748
Version: 0b16521f95c875e79d657cb8d6911c15080dbb80
Version: 6.13.8   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/virt/coco/sev-guest/sev-guest.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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            },
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              "status": "affected",
              "version": "6.13.8",
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            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/virt/coco/sev-guest/sev-guest.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.14"
            },
            {
              "lessThan": "6.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.33",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.33",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.10",
                  "versionStartIncluding": "6.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "6.13.8",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvirt: sev-guest: Do not use host-controlled page order in cleanup path\n\nWhen issuing an extended guest request (SVM_VMGEXIT_EXT_GUEST_REQUEST),\nget_ext_report() allocates a buffer to retrieve a certificate blob from the\nhost, keeping track of its size in report_req-\u003ecerts_len.\n\nHowever, the host may return SNP_GUEST_VMM_ERR_INVALID_LEN, indicating\nan invalid buffer size, as well as the expected length of such buffer.\nget_ext_report() subsequently updates report_req-\u003ecerts_len with the\nhost-controlled value, and cleans up the buffer by computing a page order\nfrom such value. This is incorrect, as the host-provided length may not\nmatch the page order of the original allocation, potentially resulting\nin corruption in the page allocator.\n\nFix this by using alloc_pages_exact() instead, and reusing @npages to\ncompute the size passed to free_pages_exact(). For consistency, also\nuse @npages to compute the size when allocating the pages, even though\nthis last change has no functional effect."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable path is reached through local guest interfaces, primarily the /dev/sev-guest SNP_GET_EXT_REPORT ioctl and the TSM configfs report path. It is not directly reachable by network packets, adjacent protocols, or physical device insertion.\nAC:L - There is no race or fragile timing requirement; the caller can request an undersized certificate buffer and the VMM can deterministically return INVALID_LEN with a mismatched npages value. The resulting wrong-order free occurs synchronously in cleanup.\nPR:L - The driver performs no capable() or namespace privilege check before dispatching SNP_GET_EXT_REPORT; exploitation only requires access to the local attestation interface. Because device-node policy may grant non-root attestation access, the higher-severity low-privilege value is appropriate.\nUI:N - No victim human action is required once a local process or attestation agent issues the request. The corrupted cleanup path is triggered automatically by the VMM response.\nS:U - The corrupted memory is guest kernel page-allocator state governed by the vulnerable guest kernel itself. This is best modeled as kernel memory corruption within the same security authority, not a guest-to-host escape.\nC:H - The wrong-order __free_pages() can return unrelated in-use pages to the allocator, creating page aliasing and plausible arbitrary kernel memory disclosure. Under the required overestimate rule, allocator corruption is treated as high confidentiality impact.\nI:H - Freeing more pages than were allocated can let later allocations overlap live kernel objects, providing a plausible write/control-flow corruption primitive. This supports high integrity impact rather than treating the bug as a mere cleanup error.\nA:H - Page allocator corruption can immediately trigger warnings, bad-page detection, oopses, or later kernel crashes. A repeatable local request can therefore cause high availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:32:09.604Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3f6fb0211b39aaa1b841260681dd02ca6b693ed5"
        },
        {
          "url": "https://git.kernel.org/stable/c/9e48b4f813d2c3db75d522aa82ab705ce04b7e2d"
        },
        {
          "url": "https://git.kernel.org/stable/c/23e6a1ca04ae44806439a5a446e62e4d42e80bb4"
        }
      ],
      "title": "virt: sev-guest: Do not use host-controlled page order in cleanup path",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-52959",
    "datePublished": "2026-06-24T16:28:40.391Z",
    "dateReserved": "2026-06-09T07:44:35.373Z",
    "dateUpdated": "2026-08-05T12:32:09.604Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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