CVE-2026-43497 (GCVE-0-2026-43497)
Vulnerability from cvelistv5
Published
2026-05-21 12:12
Modified
2026-08-05 12:28
Severity ?
7.3 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free dlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages to userspace but sets no vm_ops on the VMA. This means the kernel cannot track active mmaps. When dlfb_realloc_framebuffer() replaces the backing buffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated. On USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages while userspace PTEs still reference them, resulting in a use-after-free: the process retains read/write access to freed kernel pages. Add vm_operations_struct with open/close callbacks that maintain an atomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(), check mmap_count and return -EBUSY if the buffer is currently mapped, preventing buffer replacement while userspace holds stale PTEs. Tested with PoC using dummy_hcd + raw_gadget USB device emulation.
References
Impacted products
Vendor Product Version
Linux Linux Version: 7433914efd584b22bb49d3e1eee001f5d0525ecd
Version: 7433914efd584b22bb49d3e1eee001f5d0525ecd
Version: 7433914efd584b22bb49d3e1eee001f5d0525ecd
Version: 7433914efd584b22bb49d3e1eee001f5d0525ecd
Version: 7433914efd584b22bb49d3e1eee001f5d0525ecd
Version: 7433914efd584b22bb49d3e1eee001f5d0525ecd
Version: 7433914efd584b22bb49d3e1eee001f5d0525ecd
Version: 7433914efd584b22bb49d3e1eee001f5d0525ecd
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/video/fbdev/udlfb.c",
            "include/video/udlfb.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "60f711cfd580f86fea8284146ac133804e728f9a",
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              "versionType": "git"
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            }
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/video/fbdev/udlfb.c",
            "include/video/udlfb.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.19"
            },
            {
              "lessThan": "4.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.258",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.209",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.175",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.140",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.88",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.30",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.0.*",
              "status": "unaffected",
              "version": "7.0.7",
              "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": "5.10.258",
                  "versionStartIncluding": "4.19",
                  "vulnerable": true
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.209",
                  "versionStartIncluding": "4.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.175",
                  "versionStartIncluding": "4.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.140",
                  "versionStartIncluding": "4.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.88",
                  "versionStartIncluding": "4.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.30",
                  "versionStartIncluding": "4.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0.7",
                  "versionStartIncluding": "4.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1",
                  "versionStartIncluding": "4.19",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free\n\ndlfb_ops_mmap() uses remap_pfn_range() to map vmalloc framebuffer pages\nto userspace but sets no vm_ops on the VMA. This means the kernel cannot\ntrack active mmaps. When dlfb_realloc_framebuffer() replaces the backing\nbuffer via FBIOPUT_VSCREENINFO, existing mmap PTEs are not invalidated.\nOn USB disconnect, dlfb_ops_destroy() calls vfree() on the old pages\nwhile userspace PTEs still reference them, resulting in a use-after-free:\nthe process retains read/write access to freed kernel pages.\n\nAdd vm_operations_struct with open/close callbacks that maintain an\natomic mmap_count on struct dlfb_data. In dlfb_realloc_framebuffer(),\ncheck mmap_count and return -EBUSY if the buffer is currently mapped,\npreventing buffer replacement while userspace holds stale PTEs.\n\nTested with PoC using dummy_hcd + raw_gadget USB device emulation."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.3,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The entire exploit is driven by local syscalls (open/mmap/FBIOPUT_VSCREENINFO/close) on the /dev/fbN character device; the attacker is a local software user, not a malicious USB device feeding crafted data, so the vector to the vulnerable component is local rather than physical.\nAC:L - The attacker reliably performs the mmap + realloc-via-ioctl + close sequence and can detect the disconnect before closing; the freed-page mapping is then deterministic with no race or uncontrolled memory-layout condition required to trigger the UAF.\nPR:L - Exploitation requires read/write access to the framebuffer device node, which is available to an ordinary logged-in/video-group user (or kiosk app user) but not to a fully unprivileged unauthenticated actor.\nUI:R - The freeing vfree only runs after a USB disconnect (unregister_framebuffer), so completing the exploit depends on a disconnect event (undock/unplug) performed by the user or environment rather than by the attacker\u0027s own code.\nS:U - The use-after-free corrupts kernel memory within the same security authority (the kernel); there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - The process keeps a read mapping to freed pages that are recycled for arbitrary kernel allocations, allowing disclosure of arbitrary kernel memory.\nI:H - The same mapping retains write access to the freed pages once reused by other kernel objects, providing an arbitrary-write primitive suitable for privilege escalation or control-flow hijack.\nA:H - A use-after-free of freed kernel pages readily causes memory corruption and a kernel panic/oops."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:28:19.915Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/60f711cfd580f86fea8284146ac133804e728f9a"
        },
        {
          "url": "https://git.kernel.org/stable/c/5931f5651ee32bd41b3323256b31fcc8e71336ed"
        },
        {
          "url": "https://git.kernel.org/stable/c/e3d9865dacd7435b8465848428210d0f0c673311"
        },
        {
          "url": "https://git.kernel.org/stable/c/4f312c30f0368e8d2a76aa650dff73f23490b5e7"
        },
        {
          "url": "https://git.kernel.org/stable/c/18dd358de72d57993422cbb5dfb29ccd74efe192"
        },
        {
          "url": "https://git.kernel.org/stable/c/da9b065cedfd3b574f229d5be594e6aa47a27ae6"
        },
        {
          "url": "https://git.kernel.org/stable/c/a2c53a3822ee26e8d758071815b9ed3bf6669fc1"
        },
        {
          "url": "https://git.kernel.org/stable/c/8de779dc40d35d39fa07387b6f921eb11df0f511"
        }
      ],
      "title": "fbdev: udlfb: add vm_ops to dlfb_ops_mmap to prevent use-after-free",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43497",
    "datePublished": "2026-05-21T12:12:47.150Z",
    "dateReserved": "2026-05-01T14:12:56.013Z",
    "dateUpdated": "2026-08-05T12:28:19.915Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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