194 lines
9.9 KiB
JSON
194 lines
9.9 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2021-47394",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2024-05-21T14:58:30.814Z",
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"datePublished": "2024-05-21T15:03:51.503Z",
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"dateUpdated": "2026-08-05T08:47:37.812Z"
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"dateUpdated": "2026-08-05T08:47:37.812Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"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."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"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."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"net/netfilter/nf_tables_api.c"
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],
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{
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"programFiles": [
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"net/netfilter/nf_tables_api.c"
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],
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"versions": [
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{
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"version": "5.12",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "5.12",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "5.14.10",
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"lessThanOrEqual": "5.14.*",
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"status": "unaffected",
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},
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{
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"version": "5.15",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"versionStartIncluding": "5.12",
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}
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],
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"title": "netfilter: nf_tables: unlink table before deleting it",
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"type": "ssvc",
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"content": {
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"id": "CVE-2021-47394",
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"role": "CISA Coordinator",
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{
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"Exploitation": "none"
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"version": "2.0.3",
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"timestamp": "2024-05-28T18:27:57.258962Z"
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