CVE-2026-63856 (GCVE-0-2026-63856)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:04 – Updated: 2026-08-05 12:36
VLAI
Title
drm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings
Summary
In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings VCN encoder and decoder rings do not support 64-bit user fence writes, reject CS submissions with user fences. (cherry picked from commit e2b5499fca55f1a32960a311bbb62e35891eaf73)
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1b61de45dfaff00b627e47349a019658e39268b9 , < f264019be80de79f84f464846451445923bffea0 (git)
Affected: 1b61de45dfaff00b627e47349a019658e39268b9 , < 5e777bc4cbe928ac0fd95e368fee1540f2ce4db2 (git)
Affected: 1b61de45dfaff00b627e47349a019658e39268b9 , < ac06ce5cac9e711281585d09d00c6efcd9b86396 (git)
Affected: 1b61de45dfaff00b627e47349a019658e39268b9 , < c71aecae98e42dcf2baf462df50b3a2cf1a93fe4 (git)
Affected: 1b61de45dfaff00b627e47349a019658e39268b9 , < 8d80b293b41fcb5e9396db93e788b0f4ebcbafb7 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 6.6.141 , ≤ 6.6.* (semver)
Unaffected: 6.12.91 , ≤ 6.12.* (semver)
Unaffected: 6.18.33 , ≤ 6.18.* (semver)
Unaffected: 7.0.10 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/amd/amdgpu/vcn_v2_0.c"
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          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/amd/amdgpu/vcn_v2_0.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "5.3"
            },
            {
              "lessThan": "5.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.141",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.91",
              "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": "6.6.141",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.91",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.33",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.10",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings\n\nVCN encoder and decoder rings do not support 64-bit user fence writes,\nreject CS submissions with user fences.\n\n(cherry picked from commit e2b5499fca55f1a32960a311bbb62e35891eaf73)"
        }
      ],
      "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 - Exploitation requires submitting a crafted AMDGPU_CS ioctl to a local DRM render node (/dev/dri/renderD*); the vulnerable VCN v2.0 path is not reachable over the network.\nAC:L - An attacker with render-node access can reliably submit a VCN DEC/ENC command stream with an AMDGPU_CHUNK_ID_FENCE user-fence chunk; no race or victim-specific timing is required beyond having a VCN 2.0-capable AMDGPU.\nPR:L - Any unprivileged local user who can open the DRM render node (typical render-group membership on Linux desktops, or any app granted GPU access on RDNA1 systems) can trigger the bug without root or capabilities.\nUI:N - No victim interaction is needed; the attacker directly crafts and submits the malicious command submission via the AMDGPU DRM ioctl interface.\nS:U - The misdirected GPU fence write is constrained to the attacker\u0027s own GPU virtual address space via per-process amdgpu_vm page tables; impact remains within the same kernel/OS security authority, not a VM-guest-to-host or IOMMU-boundary escape.\nC:H - The unsupported 64-bit user fence causes the VCN engine to perform a misdirected GPU memory write (40-bit address truncation on the decoder ring), which is memory corruption that can be leveraged to corrupt adjacent GPU buffers and disclose their prior contents when read back.\nI:H - The VCN hardware performs a GPU-initiated write of the fence sequence to a potentially mis-targeted GPU virtual address, providing a memory-corruption write primitive within the submitter\u0027s GPU mappings that could be chained for further exploitation.\nA:H - Submitting an unsupported user fence to VCN rings can hang the video engine or trigger a GPU fault/reset (amdgpu_gpu_reset), denying GPU service to all local consumers including the display stack."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:36:34.905Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f264019be80de79f84f464846451445923bffea0"
        },
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          "url": "https://git.kernel.org/stable/c/5e777bc4cbe928ac0fd95e368fee1540f2ce4db2"
        },
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        },
        {
          "url": "https://git.kernel.org/stable/c/8d80b293b41fcb5e9396db93e788b0f4ebcbafb7"
        }
      ],
      "title": "drm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings",
      "x_generator": {
        "engine": "bippy-1.2.0"
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63856",
    "datePublished": "2026-07-19T14:04:45.716Z",
    "dateReserved": "2026-07-19T07:54:57.016Z",
    "dateUpdated": "2026-08-05T12:36:34.905Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
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      "date": "2026-09-20",
      "epss": "0.00132",
      "percentile": "0.03147"
    },
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                ],
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                "vendor": "Linux",
                "versions": [
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings\n\nVCN encoder and decoder rings do not support 64-bit user fence writes,\nreject CS submissions with user fences.\n\n(cherry picked from commit e2b5499fca55f1a32960a311bbb62e35891eaf73)"
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        ],
        "id": "CVE-2026-63856",
        "lastModified": "2026-07-27T17:44:23.777",
        "metrics": {
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              "cvssData": {
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                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
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              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-07-19T15:16:52.440",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Awaiting Analysis"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-31T18:48:11+00:00",
      "cve": "CVE-2026-63856",
      "id": "CVE-2026-63856",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_affected": "198",
      "product_status:known_not_affected": "76",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: drm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63856.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-18T00:47:20Z",
      "cve": "CVE-2026-63856",
      "id": "CVE-2026-63856",
      "initial_release_date": "2026-07-24T16:21:46Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "578",
      "product_status:known_not_affected": "143",
      "product_status:recommended": "250",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-63856",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63856.json",
      "version": "9"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.
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  • 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.


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