{ "schema_version": "1.6.1", "id": "RPI-CVE-2024-42109", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2024-42109" ], "published": "2024-07-30T07:47:52Z", "summary": "netfilter: nf_tables: unconditionally flush pending work before notifier", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_tables: unconditionally flush pending work before notifier\n\nsyzbot reports:\n\nKASAN: slab-uaf in nft_ctx_update include/net/netfilter/nf_tables.h:1831\nKASAN: slab-uaf in nft_commit_release net/netfilter/nf_tables_api.c:9530\nKASAN: slab-uaf int nf_tables_trans_destroy_work+0x152b/0x1750 net/netfilter/nf_tables_api.c:9597\nRead of size 2 at addr ffff88802b0051c4 by task kworker/1:1/45\n[..]\nWorkqueue: events nf_tables_trans_destroy_work\nCall Trace:\n nft_ctx_update include/net/netfilter/nf_tables.h:1831 [inline]\n nft_commit_release net/netfilter/nf_tables_api.c:9530 [inline]\n nf_tables_trans_destroy_work+0x152b/0x1750 net/netfilter/nf_tables_api.c:9597\n\nProblem is that the notifier does a conditional flush, but its possible\nthat the table-to-be-removed is still referenced by transactions being\nprocessed by the worker, so we need to flush unconditionally.\n\nWe could make the flush_work depend on whether we found a table to delete\nin nf-next to avoid the flush for most cases.\n\nAFAICS this problem is only exposed in nf-next, with\ncommit e169285f8c56 (\"netfilter: nf_tables: do not store nft_ctx in transaction objects\"),\nwith this commit applied there is an unconditional fetch of\ntable->family which is whats triggering the above splat.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.54-1+rpt2", "1:6.1.58-1+rpt2", "1:6.1.63-1+rpt1", "1:6.1.73-1+rpt1", "1:6.6.20-1+rpt1", "1:6.6.28-1+rpt1", "1:6.6.31-1+rpt1" ], "ecosystem_specific": { 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"linux-image-6.6.31+rpt-rpi-v7l", "binary_version": "1:6.6.31-1+rpt1" }, { "binary_name": "linux-image-6.6.31+rpt-rpi-v8", "binary_version": "1:6.6.31-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.1.54-1+rpt2": { "linux_commit": "2906f7abdc03d4a92b6b0e2e0c87ea2a9dffe8f7", "upstream_version": "6.1.54", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.98" }, "1:6.1.58-1+rpt2": { "linux_commit": "ccf1586ad0663fa91238ac56abf6340d6d740d18", "upstream_version": "6.1.58", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.98" }, "1:6.1.63-1+rpt1": { "linux_commit": null, "upstream_version": "6.1.63", "assessment": "upstream version (no usable Linux commit)", "upstream_fixed": "6.1.98" }, "1:6.1.73-1+rpt1": { "linux_commit": null, "upstream_version": "6.1.73", "assessment": "upstream version (no usable Linux commit)", "upstream_fixed": "6.1.98" }, "1:6.6.20-1+rpt1": { "linux_commit": "6f16847710cc0502450788b9f12f0a14d3429668", "upstream_version": "6.6.20", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.39" }, "1:6.6.28-1+rpt1": { "linux_commit": "0c341f47adc3578cd5f817aa20ee2b7f9ae6b23e", "upstream_version": "6.6.28", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.39" }, "1:6.6.31-1+rpt1": { "linux_commit": "c1432b4bae5b6582f4d32ba381459f33c34d1424", "upstream_version": "6.6.31", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.6.39" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2024-42109" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/3325628cb36b7f216c5716e7b5124d9dc81199e4" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/4c06c13317b9a08decedcd7aaf706691e336277c" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/55a40406aac555defe9bdd0adec9508116ce7cb1" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/09e650c3a3a7d804430260510534ccbf71c75b2e" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/9f6958ba2e902f9820c594869bd710ba74b7c4c0" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T11:52:36Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "AV:L - The vulnerable path is entered only through `sendmsg()`/`close()` on a local `AF_NETLINK`/`NETLINK_NETFILTER` socket handled by `nfnetlink_rcv_msg()`; the notifier `nft_rcv_nl_event()` fires on local socket release. There is no remote or adjacent-network route into nf_tables transaction teardown.\nAC:L - The attacker drives both halves of the race \u2014 issuing the nftables commit that queues transactions to `nf_tables_destroy_list` and schedule `trans_destroy_work`, then closing the owning netlink socket \u2014 and the worker's `list_splice_init()` plus `synchronize_rcu()` leaves a millisecond-wide window in which `list_empty()` is falsely true. The sequence is deterministic to set up and infinitely retryable, and syzbot produced a working reproducer.\nPR:L - The only check is `netlink_net_capable(skb, CAP_NET_ADMIN)`, which is `ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)` \u2014 satisfied by any unprivileged user via `unshare -Urn` on distros with unprivileged user namespaces enabled. No real root in the init namespace is required.\nUI:N - The attacker performs the entire sequence \u2014 table creation with `NFT_TABLE_F_OWNER`, the delete commit, and the socket close \u2014 from its own process with no victim involvement.\nS:U - The freed object and all its dereferences live in kernel memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - This is a confirmed slab use-after-free read of the `nft_table` object (`kmalloc-cg-*`, syzbot: \"Read of size 2\"); an attacker can reoccupy the freed slot by heap spraying and have the worker read attacker-chosen data, including the `ctx->table->name` pointer consumed by `nft_compat`, yielding an information-disclosure primitive.\nI:H - The dangling `trans->ctx.table` is fed to `nft_set_destroy()`, `nf_tables_chain_destroy()`, `nft_obj_destroy()` and every expression `->destroy()` callback, so a reclaimed slot lets the attacker steer subsequent frees, refcount decrements, and function-pointer-driven teardown \u2014 a classic UAF path to controlled writes and control-flow hijack.\nA:H - Even unexploited, the use-after-free corrupts kernel state inside a workqueue context and reliably produces an oops/panic, as demonstrated by the syzbot KASAN splat in `nf_tables_trans_destroy_work`." } } }