CVE-2025-23142 (GCVE-0-2025-23142)
Vulnerability from cvelistv5
Published
2025-05-01 12:55
Modified
2026-08-05 11:57
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: sctp: detect and prevent references to a freed transport in sendmsg sctp_sendmsg() re-uses associations and transports when possible by doing a lookup based on the socket endpoint and the message destination address, and then sctp_sendmsg_to_asoc() sets the selected transport in all the message chunks to be sent. There's a possible race condition if another thread triggers the removal of that selected transport, for instance, by explicitly unbinding an address with setsockopt(SCTP_SOCKOPT_BINDX_REM), after the chunks have been set up and before the message is sent. This can happen if the send buffer is full, during the period when the sender thread temporarily releases the socket lock in sctp_wait_for_sndbuf(). This causes the access to the transport data in sctp_outq_select_transport(), when the association outqueue is flushed, to result in a use-after-free read. This change avoids this scenario by having sctp_transport_free() signal the freeing of the transport, tagging it as "dead". In order to do this, the patch restores the "dead" bit in struct sctp_transport, which was removed in commit 47faa1e4c50e ("sctp: remove the dead field of sctp_transport"). Then, in the scenario where the sender thread has released the socket lock in sctp_wait_for_sndbuf(), the bit is checked again after re-acquiring the socket lock to detect the deletion. This is done while holding a reference to the transport to prevent it from being freed in the process. If the transport was deleted while the socket lock was relinquished, sctp_sendmsg_to_asoc() will return -EAGAIN to let userspace retry the send. The bug was found by a private syzbot instance (see the error report [1] and the C reproducer that triggers it [2]).
References
Impacted products
Vendor Product Version
Linux Linux Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: df132eff463873e14e019a07f387b4d577d6d1f9
Version: 26e51e5287eed4d96ea66a3da95429f42940f013
Version: 8b97e045bd6d37f96f161e4d371ae174148e1587
Version: e044554e97e812eb257d073bcc130e0ea653858f
Version: 8376fdc999be008f0e9918db52f1ed8c08f5a1c9
Version: cd947138e8c31e8cfcd489c12e9b97271beb6e79
Version: 3.18.128   ≤
Version: 4.4.166   ≤
Version: 4.9.142   ≤
Version: 4.14.85   ≤
Version: 4.19.6   ≤
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: detect and prevent references to a freed transport in sendmsg\n\nsctp_sendmsg() re-uses associations and transports when possible by\ndoing a lookup based on the socket endpoint and the message destination\naddress, and then sctp_sendmsg_to_asoc() sets the selected transport in\nall the message chunks to be sent.\n\nThere\u0027s a possible race condition if another thread triggers the removal\nof that selected transport, for instance, by explicitly unbinding an\naddress with setsockopt(SCTP_SOCKOPT_BINDX_REM), after the chunks have\nbeen set up and before the message is sent. This can happen if the send\nbuffer is full, during the period when the sender thread temporarily\nreleases the socket lock in sctp_wait_for_sndbuf().\n\nThis causes the access to the transport data in\nsctp_outq_select_transport(), when the association outqueue is flushed,\nto result in a use-after-free read.\n\nThis change avoids this scenario by having sctp_transport_free() signal\nthe freeing of the transport, tagging it as \"dead\". In order to do this,\nthe patch restores the \"dead\" bit in struct sctp_transport, which was\nremoved in\ncommit 47faa1e4c50e (\"sctp: remove the dead field of sctp_transport\").\n\nThen, in the scenario where the sender thread has released the socket\nlock in sctp_wait_for_sndbuf(), the bit is checked again after\nre-acquiring the socket lock to detect the deletion. This is done while\nholding a reference to the transport to prevent it from being freed in\nthe process.\n\nIf the transport was deleted while the socket lock was relinquished,\nsctp_sendmsg_to_asoc() will return -EAGAIN to let userspace retry the\nsend.\n\nThe bug was found by a private syzbot instance (see the error report [1]\nand the C reproducer that triggers it [2])."
        }
      ],
      "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 - The reproduced trigger is a pair of local syscalls on the attacker\u0027s own SCTP socket \u2014 a blocking sendmsg() parked in sctp_wait_for_sndbuf() plus a concurrent setsockopt(SCTP_SOCKOPT_BINDX_REM) that frees the selected transport. No remote peer input is required to drive the bug; this matches the repo\u0027s scoring of the structurally identical sctp_wait_for_connect() lock-drop UAF (CVE-2026-63971).\nAC:L - The attacker controls both sides of the race and does not need to win a tight window: shrinking SO_SNDBUF forces the sender to sleep in sctp_wait_for_sndbuf() with the socket lock released, and the second thread can issue BINDX_REM at any point during that arbitrarily long sleep, making the use-after-free essentially deterministic.\nPR:L - Creating an SCTP socket and calling sctp_bindx()/SCTP_ASCONF_SUPPORTED requires no capability \u2014 the only ns_capable() checks in net/sctp/socket.c are CAP_NET_BIND_SERVICE for privileged ports, which the attacker avoids by binding a high port. Any unprivileged local user with the sctp module available can run the published reproducer.\nUI:N - The attacking process performs every step itself within its own threads; no victim action, configuration change, or interaction with another user is needed.\nS:U - The corruption is confined to kernel slab memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - This is a slab use-after-free on a kzalloc\u0027d sctp_transport with a long, attacker-controlled reallocation window, and the freed object\u0027s asoc/dst/packet pointers are dereferenced \u2014 allowing a sprayed replacement object to be used to read arbitrary kernel memory, well beyond the bounded KASAN read that was reported.\nI:H - The freed transport is not merely read: sctp_outq_select_transport() performs list_add_tail() into the freed object\u0027s send_ready field, and sctp_packet_config()/sctp_transport_burst_limited() write vtag, max_size, size, overhead, cwnd and burst_limited into it, yielding controlled writes into a reallocated slab object suitable for control-flow hijacking.\nA:H - The bug was found as a KASAN slab-use-after-free with a reproducer, and dereferencing a freed transport\u0027s asoc/dst pointers or corrupting the send_ready list readily produces a kernel oops or panic, which an unprivileged user can trigger repeatedly."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T11:57:01.863Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/547762250220325d350d0917a7231480e0f4142b"
        },
        {
          "url": "https://git.kernel.org/stable/c/3257386be6a7eb8a8bfc9cbfb746df4eb4fc70e8"
        },
        {
          "url": "https://git.kernel.org/stable/c/0f7df4899299ce4662e5f95badb9dbc57cc37fa5"
        },
        {
          "url": "https://git.kernel.org/stable/c/7a63f4fb0efb4e69efd990cbb740a848679ec4b0"
        },
        {
          "url": "https://git.kernel.org/stable/c/c6fefcb71d246baaf3bacdad1af7ff50ebcfe652"
        },
        {
          "url": "https://git.kernel.org/stable/c/9e7c37fadb3be1fc33073fcf10aa96d166caa697"
        },
        {
          "url": "https://git.kernel.org/stable/c/5bc83bdf5f5b8010d1ca5a4555537e62413ab4e2"
        },
        {
          "url": "https://git.kernel.org/stable/c/2e5068b7e0ae0a54f6cfd03a2f80977da657f1ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/f1a69a940de58b16e8249dff26f74c8cc59b32be"
        }
      ],
      "title": "sctp: detect and prevent references to a freed transport in sendmsg",
      "x_generator": {
        "engine": "bippy-1.2.0"
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    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-23142",
    "datePublished": "2025-05-01T12:55:32.614Z",
    "dateReserved": "2025-01-11T14:28:41.512Z",
    "dateUpdated": "2026-08-05T11:57:01.863Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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