{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-40133",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-40133"
  ],
  "published": "2025-11-12T10:24:04Z",
  "summary": "mptcp: Use __sk_dst_get() and dst_dev_rcu() in mptcp_active_enable().",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: Use __sk_dst_get() and dst_dev_rcu() in mptcp_active_enable().\n\nmptcp_active_enable() is called from subflow_finish_connect(),\nwhich is icsk->icsk_af_ops->sk_rx_dst_set() and it's not always\nunder RCU.\n\nUsing sk_dst_get(sk)->dev could trigger UAF.\n\nLet's use __sk_dst_get() and dst_dev_rcu().",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/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-2025-40133"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ad16235c9d3ef7ec17c109ff39b7504f49d17072"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/cc976ec9e38bb79409de3261ba1dbb6868e2a53e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/893c49a78d9f85e4b8081b908fb7c407d018106a"
    }
  ],
  "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": 8.1,
      "cvss_v3_severity": "High",
      "scenario": "AV:N - The stale `dst->dev` dereference executes while processing a remote peer's SYN-ACK \u2014 `tcp_finish_connect()` \u2192 `icsk_af_ops->sk_rx_dst_set()` \u2192 `subflow_finish_connect()` \u2192 `mptcp_active_enable()` \u2014 so remote network data drives entry into the vulnerable code, and the peer also controls the MP_CAPABLE/blackhole state that unlocks the guarded block. Any MPTCP-enabled host making outbound connections (mobile/carrier stacks, mptcpize'd services, MPTCP proxies) is exposed to a malicious or on-path server.\nAC:H - The attacker controls one side of the race (when the SYN-ACK arrives and thus when `dst->dev` is read), but the other side requires the route's `net_device` to be concurrently unregistered so `dst_dev_put()`/`netdev_ref_replace()` drops the last reference and `free_netdev()` runs \u2014 a local netdev-teardown event a remote peer can neither induce nor time, as is landing the SYN-ACK in the socket backlog (non-RCU process context) rather than softirq.\nPR:N - The vulnerable code runs during the TCP/MPTCP handshake itself, before any application-level authentication or credential exchange, so the remote peer needs no privileges or account of any kind on the target.\nUI:N - Outbound MPTCP connections are made automatically by daemons, mobile connectivity stacks, and proxies without any human action, and an on-path attacker can simply inject the MP_CAPABLE SYN-ACK for a connection the host initiates on its own.\nS:U - The use-after-free is on a kernel `struct net_device` and its effects stay within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - This is a use-after-free read of a freed, heap-sprayable `net_device`, and a reclaimed slab can be groomed with attacker-influenced data, giving a read primitive over reclaimed kernel memory; the value read (`dev->flags & IFF_LOOPBACK`) further acts as an oracle since it determines whether `active_disable_times` is cleared, which is observable through subsequent MPTCP fallback behaviour and the MPTCP MIB counters.\nI:H - A use-after-free on a `net_device` is a heap-corruption primitive whose reclaimed contents are attacker-influenceable via spraying, and here freed memory directly steers a kernel state write (`atomic_set(&pernet->active_disable_times, 0)`), letting uncontrolled reclaimed data modify per-namespace MPTCP protocol state and, once the slab is groomed, be escalated toward arbitrary write and control-flow hijack.\nA:H - Dereferencing a freed `net_device` \u2014 allocated with `kvzalloc` and potentially unmapped on free \u2014 reliably produces a kernel oops or panic even when not weaponized, and the trigger can be retried indefinitely for a persistent denial of service."
    }
  }
}