{"id":"CVE-2026-68338","state":"PUBLISHED","title":"net/packet: avoid fanout hook re-registration after unregister","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: avoid fanout hook re-registration after unregister\n\npacket_set_ring() temporarily detaches a socket from packet delivery while\nreconfiguring its ring. It records the previous running state, clears\npo->num, unregisters the protocol hook when needed, drops po->bind_lock,\nand later restores po->num and re-registers the hook from the saved\nwas_running value.\n\nThat unlocked window can race with NETDEV_UNREGISTER. The notifier can\nobserve the socket as not running, skip __unregister_prot_hook(), and\ninvalidate the per-socket binding by setting po->ifindex to -1 and clearing\npo->prot_hook.dev. A one-member fanout group can still retain its shared\nfanout hook device pointer. When packet_set_ring() resumes, re-registering\nsolely from the stale was_running state can re-add the fanout hook after\nthe device has been unregistered.\n\nTreat po->ifindex == -1 as an invalidated binding after reacquiring\npo->bind_lock. This is distinct from ifindex 0, the normal\nunbound/wildcard state: ifindex -1 marks an existing device binding that\nwas invalidated when the device was unregistered. Restore po->num as\nbefore, but do not re-register the hook if device unregister already\ndetached the socket.","publishedAt":"2026-08-10T12:03:14.549Z","updatedAt":"2026-10-19T21:09:05.428Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"acb40ebfa5c4d62f84339fcbf713f2a9fd033a71","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"c820f4b7f2fa38f8769db0d0cefdd94e2721504d","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"4628efbdc7affd094181f5263e65c1062e31f15f","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"80ec024d53a05c60ad1d08968dcf745f10c1665c","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"0a052e0808e015e68144a9877e6ef42b952c49fa","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"1bc55c29cd85818e9052f17deb287d5a11fb817f","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"a885387dae7986a55bae5c77a15bdd447f64e9b9","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"50aff80475abd3533eef4320477037e6fcc6b56e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/packet/af_packet.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.1","versionType":"semver"},{"version":"5.10.265","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.148","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.101","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.42","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.6","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/packet/af_packet.c"]}],"references":["https://git.kernel.org/stable/c/acb40ebfa5c4d62f84339fcbf713f2a9fd033a71","https://git.kernel.org/stable/c/c820f4b7f2fa38f8769db0d0cefdd94e2721504d","https://git.kernel.org/stable/c/4628efbdc7affd094181f5263e65c1062e31f15f","https://git.kernel.org/stable/c/80ec024d53a05c60ad1d08968dcf745f10c1665c","https://git.kernel.org/stable/c/0a052e0808e015e68144a9877e6ef42b952c49fa","https://git.kernel.org/stable/c/1bc55c29cd85818e9052f17deb287d5a11fb817f","https://git.kernel.org/stable/c/a885387dae7986a55bae5c77a15bdd447f64e9b9","https://git.kernel.org/stable/c/50aff80475abd3533eef4320477037e6fcc6b56e"],"weaknesses":["CWE-362"],"ingestedAt":"2026-10-29T20:12:49.727Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/68xxx/CVE-2026-68338.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-68338","state":"PUBLISHED","datePublished":"2026-08-10T12:03:14.549Z","dateUpdated":"2026-10-19T21:09:05.428Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-30T09:28:09.384Z"},"containers":{"cna":{"title":"net/packet: avoid fanout hook re-registration after unregister","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: avoid fanout hook re-registration after unregister\n\npacket_set_ring() temporarily detaches a socket from packet delivery while\nreconfiguring its ring. It records the previous running state, clears\npo->num, unregisters the protocol hook when needed, drops po->bind_lock,\nand later restores po->num and re-registers the hook from the saved\nwas_running value.\n\nThat unlocked window can race with NETDEV_UNREGISTER. The notifier can\nobserve the socket as not running, skip __unregister_prot_hook(), and\ninvalidate the per-socket binding by setting po->ifindex to -1 and clearing\npo->prot_hook.dev. A one-member fanout group can still retain its shared\nfanout hook device pointer. When packet_set_ring() resumes, re-registering\nsolely from the stale was_running state can re-add the fanout hook after\nthe device has been unregistered.\n\nTreat po->ifindex == -1 as an invalidated binding after reacquiring\npo->bind_lock. This is distinct from ifindex 0, the normal\nunbound/wildcard state: ifindex -1 marks an existing device binding that\nwas invalidated when the device was unregistered. Restore po->num as\nbefore, but do not re-register the hook if device unregister already\ndetached the socket."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"acb40ebfa5c4d62f84339fcbf713f2a9fd033a71","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"c820f4b7f2fa38f8769db0d0cefdd94e2721504d","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"4628efbdc7affd094181f5263e65c1062e31f15f","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"80ec024d53a05c60ad1d08968dcf745f10c1665c","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"0a052e0808e015e68144a9877e6ef42b952c49fa","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"1bc55c29cd85818e9052f17deb287d5a11fb817f","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"a885387dae7986a55bae5c77a15bdd447f64e9b9","versionType":"git"},{"version":"dc99f600698dcac69b8f56dda9a8a00d645c5ffc","status":"affected","lessThan":"50aff80475abd3533eef4320477037e6fcc6b56e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/packet/af_packet.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.1","versionType":"semver"},{"version":"5.10.265","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.148","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.101","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.42","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.6","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/packet/af_packet.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/acb40ebfa5c4d62f84339fcbf713f2a9fd033a71"},{"url":"https://git.kernel.org/stable/c/c820f4b7f2fa38f8769db0d0cefdd94e2721504d"},{"url":"https://git.kernel.org/stable/c/4628efbdc7affd094181f5263e65c1062e31f15f"},{"url":"https://git.kernel.org/stable/c/80ec024d53a05c60ad1d08968dcf745f10c1665c"},{"url":"https://git.kernel.org/stable/c/0a052e0808e015e68144a9877e6ef42b952c49fa"},{"url":"https://git.kernel.org/stable/c/1bc55c29cd85818e9052f17deb287d5a11fb817f"},{"url":"https://git.kernel.org/stable/c/a885387dae7986a55bae5c77a15bdd447f64e9b9"},{"url":"https://git.kernel.org/stable/c/50aff80475abd3533eef4320477037e6fcc6b56e"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is triggered through local syscalls — creating an AF_PACKET socket, PACKET_FANOUT/bind setsockopt, PACKET_RX_RING setsockopt, and a netlink device unregister — with no remote packet processing involved.\nAC:L - The attacker controls both sides of the race: it issues the packet_set_ring() reconfiguration and deletes the bound netdev in its own netns, and the unlocked window spans synchronize_net() plus the ring swap, making it wide and reliably winnable.\nPR:L - AF_PACKET requires CAP_NET_RAW and device unregistration CAP_NET_ADMIN, but an unprivileged user obtains both via user+network namespaces (unshare -Urn) and can create and delete veth/dummy devices there.\nUI:N - The attacker performs every step itself — socket setup, ring reconfiguration and device teardown — with no action required from any other user.\nS:U - The stale hook registration and resulting corruption stay within the kernel's own security authority; no hypervisor, IOMMU or other trust boundary is crossed.\nC:H - The fanout packet_type is left linked into a net_device that is being torn down, a dangling registration on soon-to-be-freed memory; such stale-pointer state in the ptype lists can be leveraged for kernel memory disclosure.\nI:H - The dangling list node in the freed net_device's ptype list yields a list_del write into freed memory when the hook is later removed, a controllable write primitive typical of use-after-free exploitation.\nA:H - The re-added hook makes netdev_run_todo() hit BUG_ON(!list_empty(&dev->ptype_all)) while RTNL is held, oopsing the kernel and permanently wedging all further network configuration — a repeatable, unprivileged host-wide denial of service."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-19T16:33:38.308Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"5.10.265"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"5.15.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"6.6.148"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"6.12.101"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"6.18.42"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"7.1.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-68338","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:47:16.591778Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-362","lang":"en","type":"CWE","description":"CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T21:09:05.428Z"}}]}}}