GHSA-5VQ6-7CJ2-4M9J
Vulnerability from github – Published: 2026-05-27 12:31 – Updated: 2026-05-27 12:31In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix use-after-free in arena_vm_close on fork
arena_vm_open() only bumps vml->mmap_count but never registers the child VMA in arena->vma_list. The vml->vma always points at the parent VMA, so after parent munmap the pointer dangles. If the child then calls bpf_arena_free_pages(), zap_pages() reads the stale vml->vma triggering use-after-free.
Fix this by preventing the arena VMA from being inherited across fork with VM_DONTCOPY, and preventing VMA splits via the may_split callback.
Also reject mremap with a .mremap callback returning -EINVAL. A same-size mremap(MREMAP_FIXED) on the full arena VMA reaches copy_vma() through the following path:
check_prep_vma() - returns 0 early: new_len == old_len skips VM_DONTEXPAND check prep_move_vma() - vm_start == old_addr and vm_end == old_addr + old_len so may_split is never called move_vma() copy_vma_and_data() copy_vma() vm_area_dup() - copies vm_private_data (vml pointer) vm_ops->open() - bumps vml->mmap_count vm_ops->mremap() - returns -EINVAL, rollback unmaps new VMA
The refcount ensures the rollback's arena_vm_close does not free the vml shared with the original VMA.
{
"affected": [],
"aliases": [
"CVE-2026-45837"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-27T11:16:23Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix use-after-free in arena_vm_close on fork\n\narena_vm_open() only bumps vml-\u003emmap_count but never registers the\nchild VMA in arena-\u003evma_list. The vml-\u003evma always points at the\nparent VMA, so after parent munmap the pointer dangles. If the child\nthen calls bpf_arena_free_pages(), zap_pages() reads the stale\nvml-\u003evma triggering use-after-free.\n\nFix this by preventing the arena VMA from being inherited across\nfork with VM_DONTCOPY, and preventing VMA splits via the may_split\ncallback.\n\nAlso reject mremap with a .mremap callback returning -EINVAL. A\nsame-size mremap(MREMAP_FIXED) on the full arena VMA reaches\ncopy_vma() through the following path:\n\n check_prep_vma() - returns 0 early: new_len == old_len\n skips VM_DONTEXPAND check\n prep_move_vma() - vm_start == old_addr and\n vm_end == old_addr + old_len\n so may_split is never called\n move_vma()\n copy_vma_and_data()\n copy_vma()\n vm_area_dup() - copies vm_private_data (vml pointer)\n vm_ops-\u003eopen() - bumps vml-\u003emmap_count\n vm_ops-\u003emremap() - returns -EINVAL, rollback unmaps new VMA\n\nThe refcount ensures the rollback\u0027s arena_vm_close does not free\nthe vml shared with the original VMA.",
"id": "GHSA-5vq6-7cj2-4m9j",
"modified": "2026-05-27T12:31:23Z",
"published": "2026-05-27T12:31:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45837"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/201128fcc7b213d27ab77bc4e89488b41796480f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4fddde2a732de60bb97e3307d4eb69ac5f1d2b74"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/723b9fa930cc277c15ce6b9ec9feec828cfac9d7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d18099f19e53250f8ad2801498b88cec29d9107a"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.