{"id":"CVE-2026-45837","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-45837","generatedAt":"2026-10-28T07:04:13.737Z","title":"In 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.","description":"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->mmap_count but never registers the\nchild VMA in arena->vma_list. The vml->vma 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->vma 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->open()   - bumps vml->mmap_count\n      vm_ops->mremap()   - returns -EINVAL, rollback unmaps new VMA\n\nThe refcount ensures the rollback's arena_vm_close does not free\nthe vml shared with the original VMA.","published":"2026-05-27T11:16:23.000Z","lastModified":"2026-06-26T19:09:15.000Z","status":"Analyzed","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-416"],"affected":["linux/linux kernel"],"epss":{"score":0.00116,"percentile":0.01626,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.12%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/201128fcc7b213d27ab77bc4e89488b41796480f","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4fddde2a732de60bb97e3307d4eb69ac5f1d2b74","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/723b9fa930cc277c15ce6b9ec9feec828cfac9d7","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d18099f19e53250f8ad2801498b88cec29d9107a","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-45837","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}