net: nexthop: fix percpu use-after-free in remove_nh_grp_entry

{
  "id": "67e0839d90456b1711b2357a08cefd2eaf159fcf8b67dff37bb7fd813d002f5b",
  "url": "https://osv.dev/vulnerability/CVE-2026-43374",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net: nexthop: fix percpu use-after-free in remove_nh_grp_entry",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: net: nexthop: fix percpu use-after-free in remove_nh_grp_entry When removing a nexthop from a group, remove_nh_grp_entry() publishes the new group via rcu_assign_pointer() then immediately frees the removed entry's percpu stats with free_percpu(). However, the synchronize_net() grace period in the caller remove_nexthop_from_groups() runs after the free. RCU readers that entered before the publish still see the old group and can dereference the freed stats via nh_grp_entry_stats_inc() -> get_cpu_ptr(nhge->stats), causing a use-after-free on percpu memory. Fix by deferring the free_percpu() until after synchronize_net() in the caller. Removed entries are chained via nh_list onto a local deferred free list. After the grace period completes and all RCU readers have finished, the percpu stats are safely freed.",
    "evidence": "osv:CVE-2026-43374",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.78",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.19",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.9",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-43374",
      "aliases": [
        "CVE-2026-43374"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "f4676ea74b8549cd88dbfe2a592ce4530039e61f"
                },
                {
                  "fixed": "abf4feaee6405f1441929c6ebe7a250f2cd170a7"
                },
                {
                  "fixed": "ab5ebab9664214ba41a7633cb4e72f128204f924"
                },
                {
                  "fixed": "9e08ad731862b22a87cc55f752e16d66cdc9e231"
                },
                {
                  "fixed": "b2662e7593e94ae09b1cf7ee5f09160a3612bcb2"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43374.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.9.0"
                },
                {
                  "fixed": "6.12.78"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.19"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "6.19.9"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43374.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:24.912592115Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/9e08ad731862b22a87cc55f752e16d66cdc9e231",
        "https://git.kernel.org/stable/c/ab5ebab9664214ba41a7633cb4e72f128204f924",
        "https://git.kernel.org/stable/c/abf4feaee6405f1441929c6ebe7a250f2cd170a7",
        "https://git.kernel.org/stable/c/b2662e7593e94ae09b1cf7ee5f09160a3612bcb2",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43374.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-43374",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43374.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-43374",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 491616,
  "published_at": "2026-05-08T14:21:24.537+00:00"
}