{"api_version":"1","generated_at":"2026-04-23T01:13:35+00:00","cve":"CVE-2026-31504","urls":{"html":"https://cve.report/CVE-2026-31504","api":"https://cve.report/api/cve/CVE-2026-31504.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-31504","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-31504"},"summary":{"title":"net: fix fanout UAF in packet_release() via NETDEV_UP race","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: fix fanout UAF in packet_release() via NETDEV_UP race\n\n`packet_release()` has a race window where `NETDEV_UP` can re-register a\nsocket into a fanout group's `arr[]` array. The re-registration is not\ncleaned up by `fanout_release()`, leaving a dangling pointer in the fanout\narray.\n`packet_release()` does NOT zero `po->num` in its `bind_lock` section.\nAfter releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex`\nstill matches the bound device. A concurrent `packet_notifier(NETDEV_UP)`\nthat already found the socket in `sklist` can re-register the hook.\nFor fanout sockets, this re-registration calls `__fanout_link(sk, po)`\nwhich adds the socket back into `f->arr[]` and increments `f->num_members`,\nbut does NOT increment `f->sk_ref`.\n\nThe fix sets `po->num` to zero in `packet_release` while `bind_lock` is\nheld to prevent NETDEV_UP from linking, preventing the race window.\n\nThis bug was found following an additional audit with Claude Code based\non CVE-2025-38617.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-04-22 14:16:49","updated_at":"2026-04-22 14:16:49"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/42cfd7898eeed290c9fb73f732af1f7d6b0a703e","name":"https://git.kernel.org/stable/c/42cfd7898eeed290c9fb73f732af1f7d6b0a703e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ee642b1962caa9aa231c01abbd58bc453ae6b66e","name":"https://git.kernel.org/stable/c/ee642b1962caa9aa231c01abbd58bc453ae6b66e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/1b4c03f8892d955385c202009af7485364731bb9","name":"https://git.kernel.org/stable/c/1b4c03f8892d955385c202009af7485364731bb9","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/75fe6db23705a1d55160081f7b37db9665b1880b","name":"https://git.kernel.org/stable/c/75fe6db23705a1d55160081f7b37db9665b1880b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/ceccbfc6de720ad633519a226715989cfb065af1","name":"https://git.kernel.org/stable/c/ceccbfc6de720ad633519a226715989cfb065af1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6","name":"https://git.kernel.org/stable/c/d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/654386baef228c2992dbf604c819e4c7c35fc71b","name":"https://git.kernel.org/stable/c/654386baef228c2992dbf604c819e4c7c35fc71b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/42156f93d123436f2a27c468f18c966b7e5db796","name":"https://git.kernel.org/stable/c/42156f93d123436f2a27c468f18c966b7e5db796","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-31504","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31504","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ce06b03e60fc19c680d1bf873e779bf11c2fc518 ee642b1962caa9aa231c01abbd58bc453ae6b66e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ce06b03e60fc19c680d1bf873e779bf11c2fc518 42cfd7898eeed290c9fb73f732af1f7d6b0a703e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ce06b03e60fc19c680d1bf873e779bf11c2fc518 1b4c03f8892d955385c202009af7485364731bb9 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ce06b03e60fc19c680d1bf873e779bf11c2fc518 654386baef228c2992dbf604c819e4c7c35fc71b git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.203 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.168 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.131 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.80 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.21 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.19.11 6.19.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0 * 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the Linux kernel, the following vulnerability has been resolved:\n\nnet: fix fanout UAF in packet_release() via NETDEV_UP race\n\n`packet_release()` has a race window where `NETDEV_UP` can re-register a\nsocket into a fanout group's `arr[]` array. The re-registration is not\ncleaned up by `fanout_release()`, leaving a dangling pointer in the fanout\narray.\n`packet_release()` does NOT zero `po->num` in its `bind_lock` section.\nAfter releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex`\nstill matches the bound device. A concurrent `packet_notifier(NETDEV_UP)`\nthat already found the socket in `sklist` can re-register the hook.\nFor fanout sockets, this re-registration calls `__fanout_link(sk, po)`\nwhich adds the socket back into `f->arr[]` and increments `f->num_members`,\nbut does NOT increment `f->sk_ref`.\n\nThe fix sets `po->num` to zero in `packet_release` while `bind_lock` is\nheld to prevent NETDEV_UP from linking, preventing the race window.\n\nThis bug was found following an additional audit with Claude Code based\non CVE-2025-38617."}],"providerMetadata":{"dateUpdated":"2026-04-22T13:54:23.862Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/ee642b1962caa9aa231c01abbd58bc453ae6b66e"},{"url":"https://git.kernel.org/stable/c/42cfd7898eeed290c9fb73f732af1f7d6b0a703e"},{"url":"https://git.kernel.org/stable/c/1b4c03f8892d955385c202009af7485364731bb9"},{"url":"https://git.kernel.org/stable/c/654386baef228c2992dbf604c819e4c7c35fc71b"},{"url":"https://git.kernel.org/stable/c/75fe6db23705a1d55160081f7b37db9665b1880b"},{"url":"https://git.kernel.org/stable/c/d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6"},{"url":"https://git.kernel.org/stable/c/ceccbfc6de720ad633519a226715989cfb065af1"},{"url":"https://git.kernel.org/stable/c/42156f93d123436f2a27c468f18c966b7e5db796"}],"title":"net: fix fanout UAF in packet_release() via NETDEV_UP race","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-31504","datePublished":"2026-04-22T13:54:23.862Z","dateReserved":"2026-03-09T15:48:24.105Z","dateUpdated":"2026-04-22T13:54:23.862Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-04-22 14:16:49","lastModifiedDate":"2026-04-22 14:16:49","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"31504","Ordinal":"1","Title":"net: fix fanout UAF in packet_release() via NETDEV_UP race","CVE":"CVE-2026-31504","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"31504","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: fix fanout UAF in packet_release() via NETDEV_UP race\n\n`packet_release()` has a race window where `NETDEV_UP` can re-register a\nsocket into a fanout group's `arr[]` array. The re-registration is not\ncleaned up by `fanout_release()`, leaving a dangling pointer in the fanout\narray.\n`packet_release()` does NOT zero `po->num` in its `bind_lock` section.\nAfter releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex`\nstill matches the bound device. A concurrent `packet_notifier(NETDEV_UP)`\nthat already found the socket in `sklist` can re-register the hook.\nFor fanout sockets, this re-registration calls `__fanout_link(sk, po)`\nwhich adds the socket back into `f->arr[]` and increments `f->num_members`,\nbut does NOT increment `f->sk_ref`.\n\nThe fix sets `po->num` to zero in `packet_release` while `bind_lock` is\nheld to prevent NETDEV_UP from linking, preventing the race window.\n\nThis bug was found following an additional audit with Claude Code based\non CVE-2025-38617.","Type":"Description","Title":"net: fix fanout UAF in packet_release() via NETDEV_UP race"}]}}}