CVE-2026-63855 (GCVE-0-2026-63855)

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 v2.5 enc/dec rings
Summary
In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu/vcn: set no_user_fence for VCN v2.5 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 efc9dd5590894109bce9a0bfe1fa5592dd6b20b1)
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
Linux Linux Affected: 28c17d72072b7ce5cc13a527dcbfc045cc995e7d , < 2c6fb056567efb49f8674108b86088a1cfaa86d0 (git)
Affected: 28c17d72072b7ce5cc13a527dcbfc045cc995e7d , < 8f0ea4524dc71c6c9ec97f2711f46e12f624140f (git)
Affected: 28c17d72072b7ce5cc13a527dcbfc045cc995e7d , < 602d4c5872b25ddd4d82fb2025efb9a05b187bb3 (git)
Affected: 28c17d72072b7ce5cc13a527dcbfc045cc995e7d , < 5a3c6f76cab164a5d803084908d7050f649ab7f9 (git)
Affected: 28c17d72072b7ce5cc13a527dcbfc045cc995e7d , < 4f317863a3ab212a027d8c8c3cc3af4e3fb95704 (git)
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Linux Linux Affected: 5.4
Unaffected: 0 , < 5.4 (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)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c"
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          "product": "Linux",
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            "drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "5.4"
            },
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              "lessThan": "5.4",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
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              "version": "6.6.141",
              "versionType": "semver"
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.91",
              "versionType": "semver"
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              "version": "6.18.33",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.0.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "vulnerable": true
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/amdgpu/vcn: set no_user_fence for VCN v2.5 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 efc9dd5590894109bce9a0bfe1fa5592dd6b20b1)"
        }
      ],
      "metrics": [
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            "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 vulnerability is reached only through the local DRM_AMDGPU_CS ioctl on a /dev/dri/renderD* node; there is no network, Bluetooth, or physical-access attack path to the VCN command submission code.\nAC:L - On affected AMD Instinct MI100 systems, an attacker with render-node access can reliably submit a VCN enc/dec command buffer with a user-fence chunk using standard libdrm/amdgpu APIs, triggering the malformed 64-bit fence write without races or victim-dependent timing.\nPR:L - Exploitation requires opening the DRM render node and submitting GPU commands, which needs only local user privileges (typically membership in the render/video group) on multi-tenant GPU cloud instances, workstations, or containers with GPU access\u2014not root or capabilities obtainable only in the init namespace.\nUI:N - No victim interaction is required; the attacker directly crafts and submits the malicious command submission through the render node without needing another user to open files, mount filesystems, or perform any action.\nS:U - The misdirected GPU fence write corrupts memory within the attacker\u0027s own GPU virtual address space on the assigned device; it does not cross a VM, container, or IOMMU security boundary to affect another security authority.\nC:H - The bug causes GPU-initiated writes to an incorrectly decoded address, constituting out-of-bounds memory corruption that can be leveraged to read adjacent GPU-mapped buffers and disclose sensitive data from the attacker\u0027s or co-resident GPU allocations.\nI:H - The hardware fence completion write is an attacker-controlled 64-bit store to a mis-decoded GPU virtual address, providing an arbitrary GPU memory write primitive that could corrupt kernel-visible GTT mappings or GPU state for further exploitation.\nA:H - Misdirected fence writes to unmapped or invalid GPU addresses can cause GPU faults, engine hangs, or full GPU resets that deny video codec and compute service on the affected accelerator."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:36:33.839Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/2c6fb056567efb49f8674108b86088a1cfaa86d0"
        },
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        },
        {
          "url": "https://git.kernel.org/stable/c/4f317863a3ab212a027d8c8c3cc3af4e3fb95704"
        }
      ],
      "title": "drm/amdgpu/vcn: set no_user_fence for VCN v2.5 enc/dec rings",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63855",
    "datePublished": "2026-07-19T14:04:45.096Z",
    "dateReserved": "2026-07-19T07:54:57.016Z",
    "dateUpdated": "2026-08-05T12:36:33.839Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-63855",
      "date": "2026-08-11",
      "epss": "0.0012",
      "percentile": "0.02147"
    },
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    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-07-31T18:43:12+00:00",
      "cve": "CVE-2026-63855",
      "id": "CVE-2026-63855",
      "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 v2.5 enc/dec rings",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63855.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-10T16:26:00Z",
      "cve": "CVE-2026-63855",
      "id": "CVE-2026-63855",
      "initial_release_date": "2026-07-24T16:21:48Z",
      "product_status:first_fixed": "98",
      "product_status:known_affected": "132",
      "product_status:known_not_affected": "152",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-63855",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63855.json",
      "version": "4"
    }
  }
}



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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

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.