FKIE_CVE-2026-43497

Vulnerability from fkie_nvd - Published: 2026-05-21 13:16 - Updated: 2026-06-01 17:17
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
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/18dd358de72d57993422cbb5dfb29ccd74efe192
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4f312c30f0368e8d2a76aa650dff73f23490b5e7
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5931f5651ee32bd41b3323256b31fcc8e71336ed
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/60f711cfd580f86fea8284146ac133804e728f9a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8de779dc40d35d39fa07387b6f921eb11df0f511
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a2c53a3822ee26e8d758071815b9ed3bf6669fc1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/da9b065cedfd3b574f229d5be594e6aa47a27ae6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e3d9865dacd7435b8465848428210d0f0c673311
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{
  "cveTags": [],
  "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."
    }
  ],
  "id": "CVE-2026-43497",
  "lastModified": "2026-06-01T17:17:05.777",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.3,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.3,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-05-21T13:16:19.090",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/18dd358de72d57993422cbb5dfb29ccd74efe192"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/4f312c30f0368e8d2a76aa650dff73f23490b5e7"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5931f5651ee32bd41b3323256b31fcc8e71336ed"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/60f711cfd580f86fea8284146ac133804e728f9a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8de779dc40d35d39fa07387b6f921eb11df0f511"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a2c53a3822ee26e8d758071815b9ed3bf6669fc1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/da9b065cedfd3b574f229d5be594e6aa47a27ae6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e3d9865dacd7435b8465848428210d0f0c673311"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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