{"id":"CVE-2026-45837","state":"PUBLISHED","title":"bpf: Fix use-after-free in arena_vm_close on fork","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.","publishedAt":"2026-05-27T09:24:32.833Z","updatedAt":"2026-06-14T17:46:01.781Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"317460317a02a1af512697e6e964298dedd8a163","status":"affected","lessThan":"723b9fa930cc277c15ce6b9ec9feec828cfac9d7","versionType":"git"},{"version":"317460317a02a1af512697e6e964298dedd8a163","status":"affected","lessThan":"d18099f19e53250f8ad2801498b88cec29d9107a","versionType":"git"},{"version":"317460317a02a1af512697e6e964298dedd8a163","status":"affected","lessThan":"201128fcc7b213d27ab77bc4e89488b41796480f","versionType":"git"},{"version":"317460317a02a1af512697e6e964298dedd8a163","status":"affected","lessThan":"4fddde2a732de60bb97e3307d4eb69ac5f1d2b74","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/arena.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.9","versionType":"semver"},{"version":"6.12.88","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.30","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.7","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/arena.c"]}],"references":["https://git.kernel.org/stable/c/723b9fa930cc277c15ce6b9ec9feec828cfac9d7","https://git.kernel.org/stable/c/d18099f19e53250f8ad2801498b88cec29d9107a","https://git.kernel.org/stable/c/201128fcc7b213d27ab77bc4e89488b41796480f","https://git.kernel.org/stable/c/4fddde2a732de60bb97e3307d4eb69ac5f1d2b74"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/45xxx/CVE-2026-45837.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-45837","state":"PUBLISHED","datePublished":"2026-05-27T09:24:32.833Z","dateUpdated":"2026-06-14T17:46:01.781Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-13T15:03:33.077Z"},"containers":{"cna":{"title":"bpf: Fix use-after-free in arena_vm_close on fork","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"317460317a02a1af512697e6e964298dedd8a163","status":"affected","lessThan":"723b9fa930cc277c15ce6b9ec9feec828cfac9d7","versionType":"git"},{"version":"317460317a02a1af512697e6e964298dedd8a163","status":"affected","lessThan":"d18099f19e53250f8ad2801498b88cec29d9107a","versionType":"git"},{"version":"317460317a02a1af512697e6e964298dedd8a163","status":"affected","lessThan":"201128fcc7b213d27ab77bc4e89488b41796480f","versionType":"git"},{"version":"317460317a02a1af512697e6e964298dedd8a163","status":"affected","lessThan":"4fddde2a732de60bb97e3307d4eb69ac5f1d2b74","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/arena.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.9","versionType":"semver"},{"version":"6.12.88","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.30","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.7","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/arena.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/723b9fa930cc277c15ce6b9ec9feec828cfac9d7"},{"url":"https://git.kernel.org/stable/c/d18099f19e53250f8ad2801498b88cec29d9107a"},{"url":"https://git.kernel.org/stable/c/201128fcc7b213d27ab77bc4e89488b41796480f"},{"url":"https://git.kernel.org/stable/c/4fddde2a732de60bb97e3307d4eb69ac5f1d2b74"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-06-14T17:46:01.781Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"6.12.88"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"6.18.30"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"7.0.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}