{"id":"CVE-2025-21756","summary":"vsock: Keep the binding until socket destruction","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nvsock: Keep the binding until socket destruction\n\nPreserve sockets bindings; this includes both resulting from an explicit\nbind() and those implicitly bound through autobind during connect().\n\nPrevents socket unbinding during a transport reassignment, which fixes a\nuse-after-free:\n\n    1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2)\n    2. transport-\u003erelease() calls vsock_remove_bound() without checking if\n       sk was bound and moved to bound list (refcnt=1)\n    3. vsock_bind() assumes sk is in unbound list and before\n       __vsock_insert_bound(vsock_bound_sockets()) calls\n       __vsock_remove_bound() which does:\n           list_del_init(&vsk-\u003ebound_table); // nop\n           sock_put(&vsk-\u003esk);               // refcnt=0\n\nBUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730\nRead of size 4 at addr ffff88816b46a74c by task a.out/2057\n dump_stack_lvl+0x68/0x90\n print_report+0x174/0x4f6\n kasan_report+0xb9/0x190\n __vsock_bind+0x62e/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nAllocated by task 2057:\n kasan_save_stack+0x1e/0x40\n kasan_save_track+0x10/0x30\n __kasan_slab_alloc+0x85/0x90\n kmem_cache_alloc_noprof+0x131/0x450\n sk_prot_alloc+0x5b/0x220\n sk_alloc+0x2c/0x870\n __vsock_create.constprop.0+0x2e/0xb60\n vsock_create+0xe4/0x420\n __sock_create+0x241/0x650\n __sys_socket+0xf2/0x1a0\n __x64_sys_socket+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nFreed by task 2057:\n kasan_save_stack+0x1e/0x40\n kasan_save_track+0x10/0x30\n kasan_save_free_info+0x37/0x60\n __kasan_slab_free+0x4b/0x70\n kmem_cache_free+0x1a1/0x590\n __sk_destruct+0x388/0x5a0\n __vsock_bind+0x5e1/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nrefcount_t: addition on 0; use-after-free.\nWARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150\nRIP: 0010:refcount_warn_saturate+0xce/0x150\n __vsock_bind+0x66d/0x730\n vsock_bind+0x97/0xe0\n __sys_bind+0x154/0x1f0\n __x64_sys_bind+0x6e/0xb0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150\nRIP: 0010:refcount_warn_saturate+0xee/0x150\n vsock_remove_bound+0x187/0x1e0\n __vsock_release+0x383/0x4a0\n vsock_release+0x90/0x120\n __sock_release+0xa3/0x250\n sock_close+0x14/0x20\n __fput+0x359/0xa80\n task_work_run+0x107/0x1d0\n do_exit+0x847/0x2560\n do_group_exit+0xb8/0x250\n __x64_sys_exit_group+0x3a/0x50\n x64_sys_call+0xfec/0x14f0\n do_syscall_64+0x93/0x1b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e","modified":"2026-04-03T13:14:33.405399Z","published":"2025-02-27T02:18:11.547Z","related":["ALSA-2025:7903","ALSA-2025:8056","ALSA-2025:8057","SUSE-SU-2025:01919-1","SUSE-SU-2025:02264-1","SUSE-SU-2025:02321-1","SUSE-SU-2025:02322-1","SUSE-SU-2025:02537-1","SUSE-SU-2025:03315-1","SUSE-SU-2025:03317-1","SUSE-SU-2025:03341-1","SUSE-SU-2025:03343-1","SUSE-SU-2025:03370-1","SUSE-SU-2025:03374-1","SUSE-SU-2025:03375-1","SUSE-SU-2025:03381-1","SUSE-SU-2025:03387-1","SUSE-SU-2025:03391-1","SUSE-SU-2025:03393-1","SUSE-SU-2025:03395-1","SUSE-SU-2025:03397-1","SUSE-SU-2025:03400-1","SUSE-SU-2025:03406-1","SUSE-SU-2025:03408-1","SUSE-SU-2025:1177-1","SUSE-SU-2025:1178-1","SUSE-SU-2025:1180-1","SUSE-SU-2025:20190-1","SUSE-SU-2025:20192-1","SUSE-SU-2025:20260-1","SUSE-SU-2025:20270-1","SUSE-SU-2025:20722-1","SUSE-SU-2025:20723-1","SUSE-SU-2025:20724-1","SUSE-SU-2025:20725-1","SUSE-SU-2025:20726-1","SUSE-SU-2025:20727-1","SUSE-SU-2025:20737-1","SUSE-SU-2025:20738-1","SUSE-SU-2025:20768-1","SUSE-SU-2025:20769-1","SUSE-SU-2025:20770-1","SUSE-SU-2025:20784-1","SUSE-SU-2025:20785-1","SUSE-SU-2025:20786-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21756.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/3f43540166128951cc1be7ab1ce6b7f05c670d8b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/42b33381e5e1f2b967dc4fb4221ddb9aaf10d197"},{"type":"WEB","url":"https://git.kernel.org/stable/c/645ce25aa0e67895b11d89f27bb86c9d444c40f8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b1afd40321f1c243cffbcf40ea7ca41aca87fa5e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e48fcb403c2d0e574c19683f09399ab4cf67809c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e7754d564579a5db9c5c9f74228df5d6dd6f1173"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fcdd2242c0231032fc84e1404315c245ae56322a"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21756.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-21756"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c0cfa2d8a788fcf45df5bf4070ab2474c88d543a"},{"fixed":"e7754d564579a5db9c5c9f74228df5d6dd6f1173"},{"fixed":"e48fcb403c2d0e574c19683f09399ab4cf67809c"},{"fixed":"42b33381e5e1f2b967dc4fb4221ddb9aaf10d197"},{"fixed":"3f43540166128951cc1be7ab1ce6b7f05c670d8b"},{"fixed":"645ce25aa0e67895b11d89f27bb86c9d444c40f8"},{"fixed":"b1afd40321f1c243cffbcf40ea7ca41aca87fa5e"},{"fixed":"fcdd2242c0231032fc84e1404315c245ae56322a"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-21756.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}