CVE-2025-40139 (GCVE-0-2025-40139)

Vulnerability from cvelistv5 – Published: 2025-11-12 10:23 – Updated: 2026-09-02 12:49
VLAI
Title
smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().
Summary
In the Linux kernel, the following vulnerability has been resolved: smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set(). smc_clc_prfx_set() is called during connect() and not under RCU nor RTNL. Using sk_dst_get(sk)->dev could trigger UAF. Let's use __sk_dst_get() and dev_dst_rcu() under rcu_read_lock() after kernel_getsockname(). Note that the returned value of smc_clc_prfx_set() is not used in the caller. While at it, we change the 1st arg of smc_clc_prfx_set[46]_rcu() not to touch dst there.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a046d57da19f812216f393e7c535f5858f793ac3 , < 5a2fccc4b32c13ddde3676f9e15e1a9baa7d6fde (git)
Affected: a046d57da19f812216f393e7c535f5858f793ac3 , < 80d1fd39f4e37d836655e9f7ffccaf78925049bf (git)
Affected: a046d57da19f812216f393e7c535f5858f793ac3 , < 956c57daba55cf9ed25d9f2512883b8a1a927599 (git)
Affected: a046d57da19f812216f393e7c535f5858f793ac3 , < 0736993bfe5c7a9c744ae3fac62d769dfdae54e1 (git)
Affected: a046d57da19f812216f393e7c535f5858f793ac3 , < 935d783e5de9b64587f3adb25641dd8385e64ddb (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.11
Unaffected: 0 , < 4.11 (semver)
Unaffected: 6.1.187 , ≤ 6.1.* (semver)
Unaffected: 6.6.156 , ≤ 6.6.* (semver)
Unaffected: 6.12.108 , ≤ 6.12.* (semver)
Unaffected: 6.17.3 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().\n\nsmc_clc_prfx_set() is called during connect() and not under RCU\nnor RTNL.\n\nUsing sk_dst_get(sk)-\u003edev could trigger UAF.\n\nLet\u0027s use __sk_dst_get() and dev_dst_rcu() under rcu_read_lock()\nafter kernel_getsockname().\n\nNote that the returned value of smc_clc_prfx_set() is not used\nin the caller.\n\nWhile at it, we change the 1st arg of smc_clc_prfx_set[46]_rcu()\nnot to touch dst there."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
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              "lang": "en",
              "value": "AV:L - `smc_clc_prfx_set()` is only reached from the client side of the CLC handshake, via `connect()` on a locally created AF_SMC socket (`smc_connect` \u2192 `__smc_connect` \u2192 `smc_clc_send_proposal`). The attacker must have local code execution to initiate the connection, so the vector is Local even though the leaked bytes are subsequently sent to a remote peer.\nAC:L - The attacker drives both sides of the race \u2014 one thread loops `connect()` on AF_SMC sockets (the stale `dst-\u003edev` dereference), while another repeatedly creates and deletes net_devices to force `dst_dev_put()`/`free_netdev()`, which unprivileged users can do freely inside a user namespace with CAP_NET_ADMIN. No condition depends on state outside the attacker\u0027s influence, and the window is widened at will by using non-blocking connect so the work runs in `smc_connect_work`.\nPR:L - `smc_create()` performs no capability check and `MODULE_ALIAS_NETPROTO(PF_SMC)` lets any unprivileged user autoload the module; the netdev teardown side needs CAP_NET_ADMIN, which is obtainable by an ordinary user via `unshare -Urn` and therefore counts as Low, not High.\nUI:N - The attacker\u0027s own process performs every step \u2014 creating the SMC socket, connecting to a listener it controls, and tearing down the device \u2014 with no action required from any other user or administrator.\nS:U - The use-after-free touches the freed `net_device` slab and the `in_device`/`inet6_dev` structures it points to, all within the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed `net_device` is dereferenced and its `ifa_list`/`addr_list` walked, and a reclaimed slab can be groomed with attacker-controlled data, yielding an arbitrary kernel-memory read; worse, `smc_clc_prfx_set6_rcu()` copies up to 8 prefixes out of that freed memory into the CLC Proposal that `smc_clc_send_proposal()` transmits, exfiltrating freed kernel bytes onto the wire.\nI:H - A use-after-free on a `net_device` is a heap-corruption primitive \u2014 the reclaimed object\u0027s contents are attacker-influenceable through heap spraying and the code follows pointers out of it (`dev-\u003eip_ptr`, `dev-\u003eip6_ptr`, list heads), which can be groomed into an arbitrary write and control-flow hijack.\nA:H - Dereferencing the freed device and walking a bogus `in_dev`/`inet6_dev` address list reliably produces a kernel oops or panic, or an unbounded list walk that hangs the CPU, and the attacker can repeat the attempt indefinitely."
            }
          ]
        }
      ],
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      "title": "smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40139",
    "datePublished": "2025-11-12T10:23:24.216Z",
    "dateReserved": "2025-04-16T07:20:57.171Z",
    "dateUpdated": "2026-09-02T12:49:26.951Z",
    "state": "PUBLISHED"
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      "date": "2026-09-21",
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      "cve": "CVE-2025-40139",
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      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().",
      "url": "https://msrc.microsoft.com/csaf/vex/2025/msrc_cve-2025-40139.json",
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            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().\n\nsmc_clc_prfx_set() is called during connect() and not under RCU\nnor RTNL.\n\nUsing sk_dst_get(sk)-\u003edev could trigger UAF.\n\nLet\u0027s use __sk_dst_get() and dev_dst_rcu() under rcu_read_lock()\nafter kernel_getsockname().\n\nNote that the returned value of smc_clc_prfx_set() is not used\nin the caller.\n\nWhile at it, we change the 1st arg of smc_clc_prfx_set[46]_rcu()\nnot to touch dst there."
          }
        ],
        "id": "CVE-2025-40139",
        "lastModified": "2026-09-02T13:16:50.347",
        "metrics": {
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                "attackVector": "LOCAL",
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                "baseScore": 7.8,
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                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Deferred"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-30T08:48:08+00:00",
      "cve": "CVE-2025-40139",
      "id": "CVE-2025-40139",
      "initial_release_date": "2025-11-12T00:00:00+00:00",
      "product_status:known_affected": "232",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40139.json",
      "version": "3"
    }
  }
}



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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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