{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-47394","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-05-21T14:58:30.814Z","datePublished":"2024-05-21T15:03:51.503Z","dateUpdated":"2026-08-05T08:47:37.812Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T08:47:37.812Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_tables: unlink table before deleting it\n\nsyzbot reports following UAF:\nBUG: KASAN: use-after-free in memcmp+0x18f/0x1c0 lib/string.c:955\n nla_strcmp+0xf2/0x130 lib/nlattr.c:836\n nft_table_lookup.part.0+0x1a2/0x460 net/netfilter/nf_tables_api.c:570\n nft_table_lookup net/netfilter/nf_tables_api.c:4064 [inline]\n nf_tables_getset+0x1b3/0x860 net/netfilter/nf_tables_api.c:4064\n nfnetlink_rcv_msg+0x659/0x13f0 net/netfilter/nfnetlink.c:285\n netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504\n\nProblem is that all get operations are lockless, so the commit_mutex\nheld by nft_rcv_nl_event() isn't enough to stop a parallel GET request\nfrom doing read-accesses to the table object even after synchronize_rcu().\n\nTo avoid this, unlink the table first and store the table objects in\non-stack scratch space."}],"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 reached only through the local nfnetlink/nftables control plane (NETLINK_NETFILTER create of an owned table, lockless GET*, and socket close triggering NETLINK_URELEASE→nft_rcv_nl_event), not via remote packet processing.\nAC:L - The attacker controls both sides of the race—creating an NFT_TABLE_F_OWNER table, spamming parallel RCU GET lookups from another netlink socket, and closing the owner socket—so the post-synchronize_rcu free-while-still-linked window is reliably hittable.\nPR:L - nfnetlink_rcv() requires CAP_NET_ADMIN via netlink_net_capable() against the network namespace’s user_ns, which an unprivileged user obtains with unshare -Urn; nftables is fully usable per-netns.\nUI:N - Exploitation needs no victim action; the attacker creates the owned table, drives concurrent GET requests, and closes their own netlink socket to trigger the UAF.\nS:U - Impact is confined to the local kernel privilege boundary (heap UAF / local privilege escalation) with no VM, IOMMU, or cross-authority escape.\nC:H - The race frees the still-linked nft_table (and its name/contents) while lockless nft_table_lookup reads it via nla_strcmp; this classic UAF enables heap spray and arbitrary kernel read primitives.\nI:H - __nft_release_table destroys the table and nested objects while concurrent GET paths can still observe and follow those pointers, yielding reclaimable UAF/write primitives suitable for control-flow hijacking.\nA:H - Use-after-free of the table during GET lookup causes kernel oops/panic (as shown by the KASAN report in memcmp/nla_strcmp), and the attacker can trigger it repeatedly."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_tables_api.c"],"versions":[{"version":"6001a930ce0378b62210d4f83583fc88a903d89d","lessThan":"f65c73d3aabb87d4353e0bc4a718b5ae8c43fd04","status":"affected","versionType":"git"},{"version":"6001a930ce0378b62210d4f83583fc88a903d89d","lessThan":"a499b03bf36b0c2e3b958a381d828678ab0ffc5e","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_tables_api.c"],"versions":[{"version":"5.12","status":"affected"},{"version":"0","lessThan":"5.12","status":"unaffected","versionType":"semver"},{"version":"5.14.10","lessThanOrEqual":"5.14.*","status":"unaffected","versionType":"semver"},{"version":"5.15","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.12","versionEndExcluding":"5.14.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.12","versionEndExcluding":"5.15"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/f65c73d3aabb87d4353e0bc4a718b5ae8c43fd04"},{"url":"https://git.kernel.org/stable/c/a499b03bf36b0c2e3b958a381d828678ab0ffc5e"}],"title":"netfilter: nf_tables: unlink table before deleting it","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2021-47394","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2024-05-28T18:27:57.258962Z"}}}],"providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2024-06-04T17:13:40.569Z"}},{"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2024-08-04T05:39:59.375Z"},"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/f65c73d3aabb87d4353e0bc4a718b5ae8c43fd04","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/a499b03bf36b0c2e3b958a381d828678ab0ffc5e","tags":["x_transferred"]}]}]}}