CVE-2025-40139 (GCVE-0-2025-40139)
Vulnerability from cvelistv5
Published
2025-11-12 10:23
Modified
2026-08-05 12:08
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: a046d57da19f812216f393e7c535f5858f793ac3
Version: a046d57da19f812216f393e7c535f5858f793ac3
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/smc/smc_clc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "0736993bfe5c7a9c744ae3fac62d769dfdae54e1",
              "status": "affected",
              "version": "a046d57da19f812216f393e7c535f5858f793ac3",
              "versionType": "git"
            },
            {
              "lessThan": "935d783e5de9b64587f3adb25641dd8385e64ddb",
              "status": "affected",
              "version": "a046d57da19f812216f393e7c535f5858f793ac3",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/smc/smc_clc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.11"
            },
            {
              "lessThan": "4.11",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17.3",
                  "versionStartIncluding": "4.11",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18",
                  "versionStartIncluding": "4.11",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "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": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "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"
          },
          "scenarios": [
            {
              "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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:08:01.554Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0736993bfe5c7a9c744ae3fac62d769dfdae54e1"
        },
        {
          "url": "https://git.kernel.org/stable/c/935d783e5de9b64587f3adb25641dd8385e64ddb"
        }
      ],
      "title": "smc: Use __sk_dst_get() and dst_dev_rcu() in in smc_clc_prfx_set().",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40139",
    "datePublished": "2025-11-12T10:23:24.216Z",
    "dateReserved": "2025-04-16T07:20:57.171Z",
    "dateUpdated": "2026-08-05T12:08:01.554Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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