{
    "dataType": "CVE_RECORD",
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    "cveMetadata": {
        "cveId": "CVE-2024-26834",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2024-02-19T14:20:24.181Z",
        "datePublished": "2024-04-17T10:10:02.282Z",
        "dateUpdated": "2026-08-05T11:27:43.870Z"
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                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_flow_offload: release dst in case direct xmit path is used\n\nDirect xmit does not use it since it calls dev_queue_xmit() to send\npackets, hence it calls dst_release().\n\nkmemleak reports:\n\nunreferenced object 0xffff88814f440900 (size 184):\n  comm \"softirq\", pid 0, jiffies 4294951896\n  hex dump (first 32 bytes):\n    00 60 5b 04 81 88 ff ff 00 e6 e8 82 ff ff ff ff  .`[.............\n    21 0b 50 82 ff ff ff ff 00 00 00 00 00 00 00 00  !.P.............\n  backtrace (crc cb2bf5d6):\n    [<000000003ee17107>] kmem_cache_alloc+0x286/0x340\n    [<0000000021a5de2c>] dst_alloc+0x43/0xb0\n    [<00000000f0671159>] rt_dst_alloc+0x2e/0x190\n    [<00000000fe5092c9>] __mkroute_output+0x244/0x980\n    [<000000005fb96fb0>] ip_route_output_flow+0xc0/0x160\n    [<0000000045367433>] nf_ip_route+0xf/0x30\n    [<0000000085da1d8e>] nf_route+0x2d/0x60\n    [<00000000d1ecd1cb>] nft_flow_route+0x171/0x6a0 [nft_flow_offload]\n    [<00000000d9b2fb60>] nft_flow_offload_eval+0x4e8/0x700 [nft_flow_offload]\n    [<000000009f447dbb>] expr_call_ops_eval+0x53/0x330 [nf_tables]\n    [<00000000072e1be6>] nft_do_chain+0x17c/0x840 [nf_tables]\n    [<00000000d0551029>] nft_do_chain_inet+0xa1/0x210 [nf_tables]\n    [<0000000097c9d5c6>] nf_hook_slow+0x5b/0x160\n    [<0000000005eccab1>] ip_forward+0x8b6/0x9b0\n    [<00000000553a269b>] ip_rcv+0x221/0x230\n    [<00000000412872e5>] __netif_receive_skb_one_core+0xfe/0x110"
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                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
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                            "value": "AV:N - The expression is only valid on the `NF_INET_FORWARD` hook, so the leak is driven entirely by packets transiting the router — `ip_rcv` → `ip_forward` → `nft_do_chain` → `nft_flow_offload_eval`, exactly the kmemleak backtrace. Any remote host whose TCP/UDP traffic is routed through the box (port-forwarded service, DMZ host, or ordinary transit flow) triggers it, with no L2 adjacency required.\nAC:L - In the vulnerable configuration the leak is deterministic — every offloaded flow whose path resolves to `FLOW_OFFLOAD_XMIT_DIRECT` leaks its dst with no race, timing window, or memory-layout precondition, and the attacker controls the flow-creation rate by simply opening connections. The bridge-in-path and hardware-offload conditions that select direct xmit are the normal OpenWrt/consumer-router flowtable deployment, not a rare configuration.\nPR:N - Sending packets through a forwarding router requires no credentials, authentication, or account on the target; the conntrack entry and flow offload are created purely as a side effect of transit traffic. No privilege check exists anywhere between `netif_receive_skb` and `flow_offload_fill_route`.\nUI:N - The attacker's own packets drive the entire path; no administrator or user of the router needs to open a file, mount anything, or take any action for the leak to accumulate.\nS:U - The leaked `struct rtable` objects and the exhausted slab belong to the same kernel that contains the flawed code, and no VM, IOMMU, or sandbox boundary is crossed.\nC:N - The defect is a missing reference drop, so nothing is freed early, read out of bounds, or copied out — the orphaned dst is simply unreachable and no kernel data reaches userspace or any remote peer.\nI:N - An over-reference is the safe direction: no object is freed prematurely, overwritten, or type-confused, giving no write primitive and no influence over control flow. The offloaded flow itself continues to function correctly because direct xmit never needed the dst.\nA:H - The leak is unbounded and its rate is limited only by the unauthenticated attacker's packet rate — two packets per unique tuple permanently orphan up to two 184-byte `ip_dst_cache` objects, and neither conntrack expiry nor `nf_conntrack_max` reclaims them, so sustained transit traffic drives the router to memory exhaustion, OOM kill, and loss of forwarding. On IPv6 the inflated `dst_entries` count additionally keeps `fib6_run_gc()` permanently engaged and collapses `ip6_rt_gc_expire`, prematurely expiring legitimate routes."
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