{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-21791",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-21791"
  ],
  "published": "2025-02-27T02:18:18Z",
  "summary": "vrf: use RCU protection in l3mdev_l3_out()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nvrf: use RCU protection in l3mdev_l3_out()\n\nl3mdev_l3_out() can be called without RCU being held:\n\nraw_sendmsg()\n ip_push_pending_frames()\n  ip_send_skb()\n   ip_local_out()\n    __ip_local_out()\n     l3mdev_ip_out()\n\nAdd rcu_read_lock() / rcu_read_unlock() pair to avoid\na potential UAF.",
  "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-2025-21791"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6ccaa5797f5362a2aad6baa6ddaf4715ac2dd51e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/20a3489b396764cc9376e32a9172bee26a89dc3b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5bb4228c32261d06e4fbece37ec3828bcc005b6b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c7574740be8ce68a57d0aece24987b9be2114c3c"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c40cb5c03e37552d6eff963187109e2c3f78ef6f"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/022cac1c693add610ae76ede03adf4d9d5a2cf21"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/7b81425b517accefd46bee854d94954f5c57e019"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/6d0ce46a93135d96b7fa075a94a88fe0da8e8773"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - Both halves of the race are driven from the local system \u2014 a `sendmsg()` on a local socket for the read side, and RTNL link operations (VRF delete/unenslave) for the free side. A remote peer cannot induce the VRF teardown that arms the use-after-free.\nAC:L - The attacker controls both sides of the race and can loop them indefinitely: one thread sends UDP/raw packets out a VRF-enslaved device while another repeatedly unenslaves/deletes the VRF master, with preemption pressure raised at will. `do_vrf_del_slave()` widens the window further by unlinking the adjacency before clearing `IFF_L3MDEV_SLAVE`.\nPR:L - The transmit side needs no privileges at all (ordinary UDP sendmsg), and the VRF create/enslave/delete side needs only CAP_NET_ADMIN within a network namespace, which an unprivileged user obtains via `unshare -Urn`.\nUI:N - The attacker's own threads perform every step \u2014 socket sends and netlink link operations \u2014 with no victim action required.\nS:U - The use-after-free and its consequences are confined to the kernel's own security authority; no VM, IOMMU, or other trust boundary is crossed.\nC:H - The freed `netdev_adjacent` sits in a general kmalloc cache and is readily groomed, letting the attacker supply `upper->dev`, after which `master->l3mdev_ops` and `->l3mdev_l3_out` are read from an attacker-chosen address \u2014 an arbitrary kernel read primitive.\nI:H - The same reclaimed object yields an indirect call through an attacker-controlled function pointer with `master` as the first argument, giving control-flow hijack and thus arbitrary kernel-state modification.\nA:H - Even unweaponized, dereferencing a stale adjacency entry and calling through garbage function pointers reliably oopses or panics the kernel, and the attacker can retrigger it at will."
    }
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}