{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-63856",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-63856"
  ],
  "published": "2026-07-19T14:05:10Z",
  "summary": "drm/amdgpu/vcn: set no_user_fence for VCN v2.0 enc/dec rings",
  "details": "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)",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": null,
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-63856"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f264019be80de79f84f464846451445923bffea0"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5e777bc4cbe928ac0fd95e368fee1540f2ce4db2"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ac06ce5cac9e711281585d09d00c6efcd9b86396"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c71aecae98e42dcf2baf462df50b3a2cf1a93fe4"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/8d80b293b41fcb5e9396db93e788b0f4ebcbafb7"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T13:16:28Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "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's 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's 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."
    }
  }
}