{"id":"CVE-2026-45837","summary":"bpf: Fix use-after-free in arena_vm_close on fork","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's arena_vm_close does not free\nthe vml shared with the original VMA.","modified":"2026-07-08T07:01:43.137934171Z","published":"2026-05-27T09:24:32.833Z","related":["openSUSE-SU-2026:10954-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45837.json"},"references":[{"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"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45837.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45837"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"317460317a02a1af512697e6e964298dedd8a163"},{"fixed":"723b9fa930cc277c15ce6b9ec9feec828cfac9d7"},{"fixed":"d18099f19e53250f8ad2801498b88cec29d9107a"},{"fixed":"201128fcc7b213d27ab77bc4e89488b41796480f"},{"fixed":"4fddde2a732de60bb97e3307d4eb69ac5f1d2b74"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45837.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.9.0"},{"fixed":"6.12.88"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.30"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.7"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45837.json"}}],"schema_version":"1.7.5"}