{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-43374",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-43374"
  ],
  "published": "2026-05-08T14:22:57Z",
  "summary": "net: nexthop: fix percpu use-after-free in remove_nh_grp_entry",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: nexthop: fix percpu use-after-free in remove_nh_grp_entry\n\nWhen removing a nexthop from a group, remove_nh_grp_entry() publishes\nthe new group via rcu_assign_pointer() then immediately frees the\nremoved entry's percpu stats with free_percpu(). However, the\nsynchronize_net() grace period in the caller remove_nexthop_from_groups()\nruns after the free. RCU readers that entered before the publish still\nsee the old group and can dereference the freed stats via\nnh_grp_entry_stats_inc() -> get_cpu_ptr(nhge->stats), causing a\nuse-after-free on percpu memory.\n\nFix by deferring the free_percpu() until after synchronize_net() in the\ncaller. Removed entries are chained via nh_list onto a local deferred\nfree list. After the grace period completes and all RCU readers have\nfinished, the percpu stats are safely freed.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-43374"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/abf4feaee6405f1441929c6ebe7a250f2cd170a7"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ab5ebab9664214ba41a7633cb4e72f128204f924"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/9e08ad731862b22a87cc55f752e16d66cdc9e231"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/b2662e7593e94ae09b1cf7ee5f09160a3612bcb2"
    }
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  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T13:16:28Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The freeing side is reached through `RTM_DELNEXTHOP` over rtnetlink, which is a local netlink configuration interface. Remote packets can hit the RCU read side, but an attacker must locally trigger nexthop deletion to create the UAF.\nAC:L - A local attacker can create nexthop groups, attach routes, generate concurrent route lookups, and delete a member nexthop, controlling both sides of the race. The bug is a straightforward RCU grace-period violation rather than a condition dependent on external state.\nPR:L - The rtnetlink non-GET path requires `CAP_NET_ADMIN` in the socket's network namespace. Because this is reachable with namespaced `CAP_NET_ADMIN` via user/network namespaces on affected systems, this is Low rather than High.\nUI:N - No victim interaction is required once the attacker has local access and the needed namespace capability. The attacker can perform the netlink operations and traffic generation directly.\nS:U - The vulnerability corrupts kernel memory within the same kernel security authority. It is a kernel privilege-impact bug, not a VM escape or cross-scope boundary bypass.\nC:H - This is a use-after-free of per-CPU nexthop group statistics reachable from RCU route readers. Following kernel CVSS guidance, UAF memory corruption is treated as enabling high confidentiality impact.\nI:H - The stale reader writes packet counters and sequence state through a freed per-CPU pointer, creating memory corruption that can plausibly be shaped into write/control-flow impact. Per the required guidance, UAF is scored as High integrity impact.\nA:H - The stale dereference of freed per-CPU memory can crash or otherwise destabilize the kernel. Any kernel UAF with crash potential is High availability impact."
    }
  }
}