GHSA-233X-R9GJ-MFG9
Vulnerability from github – Published: 2026-05-21 15:34 – Updated: 2026-06-01 18:31In 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.
{
"affected": [],
"aliases": [
"CVE-2026-43497"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-21T13:16:19Z",
"severity": "HIGH"
},
"details": "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": "GHSA-233x-r9gj-mfg9",
"modified": "2026-06-01T18:31:32Z",
"published": "2026-05-21T15:34:08Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-43497"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/18dd358de72d57993422cbb5dfb29ccd74efe192"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4f312c30f0368e8d2a76aa650dff73f23490b5e7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5931f5651ee32bd41b3323256b31fcc8e71336ed"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/60f711cfd580f86fea8284146ac133804e728f9a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8de779dc40d35d39fa07387b6f921eb11df0f511"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a2c53a3822ee26e8d758071815b9ed3bf6669fc1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/da9b065cedfd3b574f229d5be594e6aa47a27ae6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e3d9865dacd7435b8465848428210d0f0c673311"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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