CVE-2025-21756

vsock: Keep the binding until socket destruction

State: Published
Severity: 7.8 High
Published: Feb 27, 2025
Updated: Oct 15, 2026
Reserved: Dec 29, 2024

Description

In the Linux kernel, the following vulnerability has been resolved:

vsock: Keep the binding until socket destruction

Preserve sockets bindings; this includes both resulting from an explicit bind() and those implicitly bound through autobind during connect().

Prevents socket unbinding during a transport reassignment, which fixes a use-after-free:

1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2) 2. transport->release() calls vsock_remove_bound() without checking if sk was bound and moved to bound list (refcnt=1) 3. vsock_bind() assumes sk is in unbound list and before __vsock_insert_bound(vsock_bound_sockets()) calls __vsock_remove_bound() which does: list_del_init(&vsk->bound_table); // nop sock_put(&vsk->sk); // refcnt=0

BUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730 Read of size 4 at addr ffff88816b46a74c by task a.out/2057 dump_stack_lvl+0x68/0x90 print_report+0x174/0x4f6 kasan_report+0xb9/0x190 __vsock_bind+0x62e/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Allocated by task 2057: kasan_save_stack+0x1e/0x40 kasan_save_track+0x10/0x30 __kasan_slab_alloc+0x85/0x90 kmem_cache_alloc_noprof+0x131/0x450 sk_prot_alloc+0x5b/0x220 sk_alloc+0x2c/0x870 __vsock_create.constprop.0+0x2e/0xb60 vsock_create+0xe4/0x420 __sock_create+0x241/0x650 __sys_socket+0xf2/0x1a0 __x64_sys_socket+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 2057: kasan_save_stack+0x1e/0x40 kasan_save_track+0x10/0x30 kasan_save_free_info+0x37/0x60 __kasan_slab_free+0x4b/0x70 kmem_cache_free+0x1a1/0x590 __sk_destruct+0x388/0x5a0 __vsock_bind+0x5e1/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

refcount_t: addition on 0; use-after-free. WARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150 RIP: 0010:refcount_warn_saturate+0xce/0x150 __vsock_bind+0x66d/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

refcount_t: underflow; use-after-free. WARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150 RIP: 0010:refcount_warn_saturate+0xee/0x150 vsock_remove_bound+0x187/0x1e0 __vsock_release+0x383/0x4a0 vsock_release+0x90/0x120 __sock_release+0xa3/0x250 sock_close+0x14/0x20 __fput+0x359/0xa80 task_work_run+0x107/0x1d0 do_exit+0x847/0x2560 do_group_exit+0xb8/0x250 __x64_sys_exit_group+0x3a/0x50 x64_sys_call+0xfec/0x14f0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Scores

CVSS	Score	Vector	Source
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	Linux
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	CISA-ADP

Weaknesses

CWE-416 Use After Free

Affected Products

Product	Versions
LinuxLinux	c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before e7754d564579a5db9c5c9f74228df5d6dd6f1173Affected c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before e48fcb403c2d0e574c19683f09399ab4cf67809cAffected c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before 42b33381e5e1f2b967dc4fb4221ddb9aaf10d197Affected c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before 3f43540166128951cc1be7ab1ce6b7f05c670d8bAffected c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before 645ce25aa0e67895b11d89f27bb86c9d444c40f8Affected c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before b1afd40321f1c243cffbcf40ea7ca41aca87fa5eAffected c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before fcdd2242c0231032fc84e1404315c245ae56322aAffected
LinuxLinux	5.5Affected before 5.5Not affected 5.10.235 through 5.10.Not affected 5.15.179 through 5.15.Not affected 6.1.131 through 6.1.Not affected 6.6.79 through 6.6.Not affected 6.12.16 through 6.12.Not affected 6.13.4 through 6.13.Not affected 6.14 and laterNot affected

Product

Versions

LinuxLinux

c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before e7754d564579a5db9c5c9f74228df5d6dd6f1173Affected
c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before e48fcb403c2d0e574c19683f09399ab4cf67809cAffected
c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before 42b33381e5e1f2b967dc4fb4221ddb9aaf10d197Affected
c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before 3f43540166128951cc1be7ab1ce6b7f05c670d8bAffected
c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before 645ce25aa0e67895b11d89f27bb86c9d444c40f8Affected
c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before b1afd40321f1c243cffbcf40ea7ca41aca87fa5eAffected
c0cfa2d8a788fcf45df5bf4070ab2474c88d543a to before fcdd2242c0231032fc84e1404315c245ae56322aAffected

LinuxLinux

5.5Affected
before 5.5Not affected
5.10.235 through 5.10.*Not affected
5.15.179 through 5.15.*Not affected
6.1.131 through 6.1.*Not affected
6.6.79 through 6.6.*Not affected
6.12.16 through 6.12.*Not affected
6.13.4 through 6.13.*Not affected
6.14 and laterNot affected

References

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