{"id":"AZL-71380","summary":"CVE-2025-40258 affecting package kernel for versions less than 6.6.119.3-1","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","modified":"2026-04-01T05:22:02.972579Z","published":"2025-12-04T16:16:19Z","upstream":["CVE-2025-40258"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-40258"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.119.3-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-71380.json"}}],"schema_version":"1.7.5"}