GHSA-86FP-6JQC-QG25
Vulnerability from github – Published: 2025-12-04 18:30 – Updated: 2026-07-30 06:32In the Linux kernel, the following vulnerability has been resolved:
mptcp: fix race condition in mptcp_schedule_work()
syzbot reported use-after-free in mptcp_schedule_work() [1]
Issue here is that mptcp_schedule_work() schedules a work, then gets a refcount on sk->sk_refcnt if the work was scheduled. This refcount will be released by mptcp_worker().
[A] if (schedule_work(...)) { [B] sock_hold(sk); return true; }
Problem is that mptcp_worker() can run immediately and complete before [B]
We need instead :
sock_hold(sk);
if (schedule_work(...))
return true;
sock_put(sk);
[1] refcount_t: addition on 0; use-after-free. WARNING: CPU: 1 PID: 29 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25 Call Trace: __refcount_add include/linux/refcount.h:-1 [inline] __refcount_inc include/linux/refcount.h:366 [inline] refcount_inc include/linux/refcount.h:383 [inline] sock_hold include/net/sock.h:816 [inline] mptcp_schedule_work+0x164/0x1a0 net/mptcp/protocol.c:943 mptcp_tout_timer+0x21/0xa0 net/mptcp/protocol.c:2316 call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747 expire_timers kernel/time/timer.c:1798 [inline] __run_timers kernel/time/timer.c:2372 [inline] __run_timer_base+0x648/0x970 kernel/time/timer.c:2384 run_timer_base kernel/time/timer.c:2393 [inline] run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403 handle_softirqs+0x22f/0x710 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] run_ktimerd+0xcf/0x190 kernel/softirq.c:1138 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
{
"affected": [],
"aliases": [
"CVE-2025-40258"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-12-04T16:16:19Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix race condition in mptcp_schedule_work()\n\nsyzbot reported use-after-free in mptcp_schedule_work() [1]\n\nIssue here is that mptcp_schedule_work() schedules a work,\nthen gets a refcount on sk-\u003esk_refcnt if the work was scheduled.\nThis refcount will be released by mptcp_worker().\n\n[A] if (schedule_work(...)) {\n[B] sock_hold(sk);\n return true;\n }\n\nProblem is that mptcp_worker() can run immediately and complete before [B]\n\nWe need instead :\n\n sock_hold(sk);\n if (schedule_work(...))\n return true;\n sock_put(sk);\n\n[1]\nrefcount_t: addition on 0; use-after-free.\n WARNING: CPU: 1 PID: 29 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25\nCall Trace:\n \u003cTASK\u003e\n __refcount_add include/linux/refcount.h:-1 [inline]\n __refcount_inc include/linux/refcount.h:366 [inline]\n refcount_inc include/linux/refcount.h:383 [inline]\n sock_hold include/net/sock.h:816 [inline]\n mptcp_schedule_work+0x164/0x1a0 net/mptcp/protocol.c:943\n mptcp_tout_timer+0x21/0xa0 net/mptcp/protocol.c:2316\n call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747\n expire_timers kernel/time/timer.c:1798 [inline]\n __run_timers kernel/time/timer.c:2372 [inline]\n __run_timer_base+0x648/0x970 kernel/time/timer.c:2384\n run_timer_base kernel/time/timer.c:2393 [inline]\n run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403\n handle_softirqs+0x22f/0x710 kernel/softirq.c:622\n __do_softirq kernel/softirq.c:656 [inline]\n run_ktimerd+0xcf/0x190 kernel/softirq.c:1138\n smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160\n kthread+0x711/0x8a0 kernel/kthread.c:463\n ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245",
"id": "GHSA-86fp-6jqc-qg25",
"modified": "2026-07-30T06:32:18Z",
"published": "2025-12-04T18:30:53Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-40258"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-253495.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/035bca3f017ee9dea3a5a756e77a6f7138cc6eea"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3fc7723ed01d1130d4bf7063c50e0af60ecccbb4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8f9ba1a99a89feef9b5867c15a0141a97e893309"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/99908e2d601236842d705d5fd04fb349577316f5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ac28dfddedf6f209190950fc71bcff65ec4ab47b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/db4f7968a75250ca6c4ed70d0a78beabb2dcee18"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f865e6595acf33083168db76921e66ace8bf0e5b"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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