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CVE-2025-21812 (GCVE-0-2025-21812)

Vulnerability from cvelistv5 – Published: 2025-02-27 20:01 – Updated: 2026-08-05 11:54
VLAI
Title
ax25: rcu protect dev->ax25_ptr
Summary
In the Linux kernel, the following vulnerability has been resolved: ax25: rcu protect dev->ax25_ptr syzbot found a lockdep issue [1]. We should remove ax25 RTNL dependency in ax25_setsockopt() This should also fix a variety of possible UAF in ax25. [1] WARNING: possible circular locking dependency detected 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Not tainted ------------------------------------------------------ syz.5.1818/12806 is trying to acquire lock: ffffffff8fcb3988 (rtnl_mutex){+.+.}-{4:4}, at: ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680 but task is already holding lock: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline] ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (sk_lock-AF_AX25){+.+.}-{0:0}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 lock_sock_nested+0x48/0x100 net/core/sock.c:3642 lock_sock include/net/sock.h:1618 [inline] ax25_kill_by_device net/ax25/af_ax25.c:101 [inline] ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146 notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85 __dev_notify_flags+0x207/0x400 dev_change_flags+0xf0/0x1a0 net/core/dev.c:9026 dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:563 dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:820 sock_do_ioctl+0x240/0x460 net/socket.c:1234 sock_ioctl+0x626/0x8e0 net/socket.c:1339 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (rtnl_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/locking/lockdep.c:3280 [inline] validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735 ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680 do_sock_setsockopt+0x3af/0x720 net/socket.c:2324 __sys_setsockopt net/socket.c:2349 [inline] __do_sys_setsockopt net/socket.c:2355 [inline] __se_sys_setsockopt net/socket.c:2352 [inline] __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2352 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sk_lock-AF_AX25); lock(rtnl_mutex); lock(sk_lock-AF_AX25); lock(rtnl_mutex); *** DEADLOCK *** 1 lock held by syz.5.1818/12806: #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline] #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574 stack backtrace: CPU: 1 UID: 0 PID: 12806 Comm: syz.5.1818 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206 check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/lockin ---truncated---
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-03-04 18:00 UTC
CWE
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: c433570458e49bccea5c551df628d058b3526289 , < 2802ed4ced27ebd474828fc67ffd7d66f11e3605 (git)
Affected: c433570458e49bccea5c551df628d058b3526289 , < 7705d8a7f2c26c80973c81093db07c6022b2b30e (git)
Affected: c433570458e49bccea5c551df628d058b3526289 , < 8937f5e38a218531dce2a89fae60e3adcc2311e1 (git)
Affected: c433570458e49bccea5c551df628d058b3526289 , < c2531db6de3c95551be58878f859c6a053b7eb2e (git)
Affected: c433570458e49bccea5c551df628d058b3526289 , < 95fc45d1dea8e1253f8ec58abc5befb71553d666 (git)
Affected: 7f93d703e276311dd289c9a520ce9e8c8fa2858c (git)
Affected: c0e93a6d36135d5082cb3af8352f5b69c9f58d6e (git)
Affected: c39b8fd4997bf99503b8e48d8cb0eedb1d9a54f0 (git)
Affected: 26a5adc8eb26d170058645c3cccd4d19165bec16 (git)
Affected: 3e881d8764ed9b04ae3e5c3e5d132acb75ef91ba (git)
Affected: 77768c96dcf860c43b970b87b2a09229f84ea560 (git)
Affected: 3.18.132 , < 3.19 (semver)
Affected: 4.4.170 , < 4.5 (semver)
Affected: 4.9.149 , < 4.10 (semver)
Affected: 4.14.92 , < 4.15 (semver)
Affected: 4.19.14 , < 4.20 (semver)
Affected: 4.20.1 , < 4.21 (semver)
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Linux Linux Affected: 5.0
Unaffected: 0 , < 5.0 (semver)
Unaffected: 6.1.129 , ≤ 6.1.* (semver)
Unaffected: 6.6.76 , ≤ 6.6.* (semver)
Unaffected: 6.12.13 , ≤ 6.12.* (semver)
Unaffected: 6.13.2 , ≤ 6.13.* (semver)
Unaffected: 6.14 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: rcu protect dev-\u003eax25_ptr\n\nsyzbot found a lockdep issue [1].\n\nWe should remove ax25 RTNL dependency in ax25_setsockopt()\n\nThis should also fix a variety of possible UAF in ax25.\n\n[1]\n\nWARNING: possible circular locking dependency detected\n6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Not tainted\n------------------------------------------------------\nsyz.5.1818/12806 is trying to acquire lock:\n ffffffff8fcb3988 (rtnl_mutex){+.+.}-{4:4}, at: ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680\n\nbut task is already holding lock:\n ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]\n ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574\n\nwhich lock already depends on the new lock.\n\nthe existing dependency chain (in reverse order) is:\n\n-\u003e #1 (sk_lock-AF_AX25){+.+.}-{0:0}:\n        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n        lock_sock_nested+0x48/0x100 net/core/sock.c:3642\n        lock_sock include/net/sock.h:1618 [inline]\n        ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]\n        ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146\n        notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85\n       __dev_notify_flags+0x207/0x400\n        dev_change_flags+0xf0/0x1a0 net/core/dev.c:9026\n        dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:563\n        dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:820\n        sock_do_ioctl+0x240/0x460 net/socket.c:1234\n        sock_ioctl+0x626/0x8e0 net/socket.c:1339\n        vfs_ioctl fs/ioctl.c:51 [inline]\n        __do_sys_ioctl fs/ioctl.c:906 [inline]\n        __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892\n        do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\n-\u003e #0 (rtnl_mutex){+.+.}-{4:4}:\n        check_prev_add kernel/locking/lockdep.c:3161 [inline]\n        check_prevs_add kernel/locking/lockdep.c:3280 [inline]\n        validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904\n        __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226\n        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n        __mutex_lock_common kernel/locking/mutex.c:585 [inline]\n        __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735\n        ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680\n        do_sock_setsockopt+0x3af/0x720 net/socket.c:2324\n        __sys_setsockopt net/socket.c:2349 [inline]\n        __do_sys_setsockopt net/socket.c:2355 [inline]\n        __se_sys_setsockopt net/socket.c:2352 [inline]\n        __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2352\n        do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nother info that might help us debug this:\n\n Possible unsafe locking scenario:\n\n       CPU0                    CPU1\n       ----                    ----\n  lock(sk_lock-AF_AX25);\n                               lock(rtnl_mutex);\n                               lock(sk_lock-AF_AX25);\n  lock(rtnl_mutex);\n\n *** DEADLOCK ***\n\n1 lock held by syz.5.1818/12806:\n  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]\n  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574\n\nstack backtrace:\nCPU: 1 UID: 0 PID: 12806 Comm: syz.5.1818 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\nCall Trace:\n \u003cTASK\u003e\n  __dump_stack lib/dump_stack.c:94 [inline]\n  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n  print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074\n  check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206\n  check_prev_add kernel/locking/lockdep.c:3161 [inline]\n  check_prevs_add kernel/lockin\n---truncated---"
        }
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              "value": "AV:L - The controllable attack path is an AF_AX25 socket driven by local syscalls (setsockopt SO_BINDTODEVICE, connect/sendmsg autobind, close), which is what both frees the ax25_dev and re-dereferences the dangling dev-\u003eax25_ptr. Although received AX.25 frames also read dev-\u003eax25_ptr in ax25_rcv(), an adjacent radio/L2 peer cannot itself cause the free, so the attacker must be local.\nAC:L - No race needs to be won: SO_BINDTODEVICE stores ax25-\u003eax25_dev without a reference while ax25_release() drops one, so a single setsockopt+close deterministically drives the refcount to zero and kfree()s the object still published in dev-\u003eax25_ptr. The pure device-down race variant is also attacker-driven by spinning setsockopt/connect in a loop.\nPR:L - ax25_create() imposes no capability check for SOCK_DGRAM/SOCK_SEQPACKET, and the AF_AX25 module autoloads via the net-pf-3 alias, so any unprivileged local user in the init namespace can reach every vulnerable path. Root is only needed for the one-time deployment setup of the AX.25 port, not by the attacker.\nUI:N - The entire sequence is performed by the attacker\u0027s own process through socket(), setsockopt(), connect()/sendmsg() and close(); no victim action is involved.\nS:U - The freed ax25_dev and the corrupted kernel heap are entirely within the kernel\u0027s own security authority, with no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - After the free, ax25_fillin_cb() copies bytes from the reclaimed slab object into the socket\u0027s t1/t2/t3/n2/paclen/window/backoff fields, which userspace reads back with getsockopt() \u2014 a direct kernel heap disclosure \u2014 and the general UAF read of ax25_dev-\u003edev/-\u003eforward enables broader information leakage.\nI:H - The dangling pointer yields repeated refcount_dec() and stores to ax25_dev-\u003eforward and -\u003edevice_up into memory that has been reallocated for other kernel objects, giving a controlled decrement/write primitive on a groomed heap that is exploitable for privilege escalation.\nA:H - Dereferencing and freeing the already-freed ax25_dev reliably produces a kernel oops/panic (and netdev refcount underflow), and the same commit fixes a genuine sk_lock-AF_AX25 versus rtnl_mutex ABBA deadlock that permanently wedges the rtnl mutex and with it the entire networking stack."
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          "url": "https://git.kernel.org/stable/c/2802ed4ced27ebd474828fc67ffd7d66f11e3605"
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      "title": "ax25: rcu protect dev-\u003eax25_ptr",
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    "datePublished": "2025-02-27T20:01:02.837Z",
    "dateReserved": "2024-12-29T08:45:45.774Z",
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: rcu protect dev-\u003eax25_ptr\n\nsyzbot found a lockdep issue [1].\n\nWe should remove ax25 RTNL dependency in ax25_setsockopt()\n\nThis should also fix a variety of possible UAF in ax25.\n\n[1]\n\nWARNING: possible circular locking dependency detected\n6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Not tainted\n------------------------------------------------------\nsyz.5.1818/12806 is trying to acquire lock:\n ffffffff8fcb3988 (rtnl_mutex){+.+.}-{4:4}, at: ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680\n\nbut task is already holding lock:\n ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]\n ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574\n\nwhich lock already depends on the new lock.\n\nthe existing dependency chain (in reverse order) is:\n\n-\u003e #1 (sk_lock-AF_AX25){+.+.}-{0:0}:\n        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n        lock_sock_nested+0x48/0x100 net/core/sock.c:3642\n        lock_sock include/net/sock.h:1618 [inline]\n        ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]\n        ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146\n        notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85\n       __dev_notify_flags+0x207/0x400\n        dev_change_flags+0xf0/0x1a0 net/core/dev.c:9026\n        dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:563\n        dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:820\n        sock_do_ioctl+0x240/0x460 net/socket.c:1234\n        sock_ioctl+0x626/0x8e0 net/socket.c:1339\n        vfs_ioctl fs/ioctl.c:51 [inline]\n        __do_sys_ioctl fs/ioctl.c:906 [inline]\n        __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892\n        do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\n-\u003e #0 (rtnl_mutex){+.+.}-{4:4}:\n        check_prev_add kernel/locking/lockdep.c:3161 [inline]\n        check_prevs_add kernel/locking/lockdep.c:3280 [inline]\n        validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904\n        __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226\n        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n        __mutex_lock_common kernel/locking/mutex.c:585 [inline]\n        __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735\n        ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680\n        do_sock_setsockopt+0x3af/0x720 net/socket.c:2324\n        __sys_setsockopt net/socket.c:2349 [inline]\n        __do_sys_setsockopt net/socket.c:2355 [inline]\n        __se_sys_setsockopt net/socket.c:2352 [inline]\n        __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2352\n        do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nother info that might help us debug this:\n\n Possible unsafe locking scenario:\n\n       CPU0                    CPU1\n       ----                    ----\n  lock(sk_lock-AF_AX25);\n                               lock(rtnl_mutex);\n                               lock(sk_lock-AF_AX25);\n  lock(rtnl_mutex);\n\n *** DEADLOCK ***\n\n1 lock held by syz.5.1818/12806:\n  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]\n  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574\n\nstack backtrace:\nCPU: 1 UID: 0 PID: 12806 Comm: syz.5.1818 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\nCall Trace:\n \u003cTASK\u003e\n  __dump_stack lib/dump_stack.c:94 [inline]\n  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n  print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074\n  check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206\n  check_prev_add kernel/locking/lockdep.c:3161 [inline]\n  check_prevs_add kernel/lockin\n---truncated---"
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ax25: rcu protect dev-\u0026gt;ax25_ptr syzbot encontr\u00f3 un problema de lockdep [1]. Deber\u00edamos eliminar la dependencia RTNL de ax25 en ax25_setsockopt(). Esto tambi\u00e9n deber\u00eda solucionar una variedad de posibles UAF en ax25. [1] ADVERTENCIA: se detect\u00f3 una posible dependencia de bloqueo circular 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Not tainted ------------------------------------------------------ syz.5.1818/12806 is trying to acquire lock: ffffffff8fcb3988 (rtnl_mutex){+.+.}-{4:4}, at: ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680 but task is already holding lock: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline] ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -\u0026gt; #1 (sk_lock-AF_AX25){+.+.}-{0:0}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 lock_sock_nested+0x48/0x100 net/core/sock.c:3642 lock_sock include/net/sock.h:1618 [inline] ax25_kill_by_device net/ax25/af_ax25.c:101 [inline] ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146 notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85 __dev_notify_flags+0x207/0x400 dev_change_flags+0xf0/0x1a0 net/core/dev.c:9026 dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:563 dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:820 sock_do_ioctl+0x240/0x460 net/socket.c:1234 sock_ioctl+0x626/0x8e0 net/socket.c:1339 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f -\u0026gt; #0 (rtnl_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/locking/lockdep.c:3280 [inline] validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849 __mutex_lock_common kernel/locking/mutex.c:585 [inline] __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735 ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680 do_sock_setsockopt+0x3af/0x720 net/socket.c:2324 __sys_setsockopt net/socket.c:2349 [inline] __do_sys_setsockopt net/socket.c:2355 [inline] __se_sys_setsockopt net/socket.c:2352 [inline] __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2352 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sk_lock-AF_AX25); lock(rtnl_mutex); lock(sk_lock-AF_AX25); lock(rtnl_mutex); *** DEADLOCK *** 1 lock held by syz.5.1818/12806: #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline] #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574 stack backtrace: CPU: 1 UID: 0 PID: 12806 Comm: syz.5.1818 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Call Trace:  __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206 check_prev_add kernel/locking/lockdep.c:3161 [inline] check_prevs_add kernel/lockin ---truncated--- "
          }
        ],
        "id": "CVE-2025-21812",
        "lastModified": "2026-06-17T08:44:20.233",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
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          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nax25: rcu protect dev-\u003eax25_ptr\n\nsyzbot found a lockdep issue [1].\n\nWe should remove ax25 RTNL dependency in ax25_setsockopt()\n\nThis should also fix a variety of possible UAF in ax25.\n\n[1]\n\nWARNING: possible circular locking dependency detected\n6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Not tainted\n------------------------------------------------------\nsyz.5.1818/12806 is trying to acquire lock:\n ffffffff8fcb3988 (rtnl_mutex){+.+.}-{4:4}, at: ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680\n\nbut task is already holding lock:\n ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]\n ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574\n\nwhich lock already depends on the new lock.\n\nthe existing dependency chain (in reverse order) is:\n\n-\u003e #1 (sk_lock-AF_AX25){+.+.}-{0:0}:\n        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n        lock_sock_nested+0x48/0x100 net/core/sock.c:3642\n        lock_sock include/net/sock.h:1618 [inline]\n        ax25_kill_by_device net/ax25/af_ax25.c:101 [inline]\n        ax25_device_event+0x24d/0x580 net/ax25/af_ax25.c:146\n        notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85\n       __dev_notify_flags+0x207/0x400\n        dev_change_flags+0xf0/0x1a0 net/core/dev.c:9026\n        dev_ifsioc+0x7c8/0xe70 net/core/dev_ioctl.c:563\n        dev_ioctl+0x719/0x1340 net/core/dev_ioctl.c:820\n        sock_do_ioctl+0x240/0x460 net/socket.c:1234\n        sock_ioctl+0x626/0x8e0 net/socket.c:1339\n        vfs_ioctl fs/ioctl.c:51 [inline]\n        __do_sys_ioctl fs/ioctl.c:906 [inline]\n        __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892\n        do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\n-\u003e #0 (rtnl_mutex){+.+.}-{4:4}:\n        check_prev_add kernel/locking/lockdep.c:3161 [inline]\n        check_prevs_add kernel/locking/lockdep.c:3280 [inline]\n        validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904\n        __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226\n        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849\n        __mutex_lock_common kernel/locking/mutex.c:585 [inline]\n        __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735\n        ax25_setsockopt+0xa55/0xe90 net/ax25/af_ax25.c:680\n        do_sock_setsockopt+0x3af/0x720 net/socket.c:2324\n        __sys_setsockopt net/socket.c:2349 [inline]\n        __do_sys_setsockopt net/socket.c:2355 [inline]\n        __se_sys_setsockopt net/socket.c:2352 [inline]\n        __x64_sys_setsockopt+0x1ee/0x280 net/socket.c:2352\n        do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nother info that might help us debug this:\n\n Possible unsafe locking scenario:\n\n       CPU0                    CPU1\n       ----                    ----\n  lock(sk_lock-AF_AX25);\n                               lock(rtnl_mutex);\n                               lock(sk_lock-AF_AX25);\n  lock(rtnl_mutex);\n\n *** DEADLOCK ***\n\n1 lock held by syz.5.1818/12806:\n  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1618 [inline]\n  #0: ffff8880617ac258 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x209/0xe90 net/ax25/af_ax25.c:574\n\nstack backtrace:\nCPU: 1 UID: 0 PID: 12806 Comm: syz.5.1818 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024\nCall Trace:\n \u003cTASK\u003e\n  __dump_stack lib/dump_stack.c:94 [inline]\n  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n  print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074\n  check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206\n  check_prev_add kernel/locking/lockdep.c:3161 [inline]\n  check_prevs_add kernel/lockin\n---truncated---"
            }
          ],
          "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 controllable attack path is an AF_AX25 socket driven by local syscalls (setsockopt SO_BINDTODEVICE, connect/sendmsg autobind, close), which is what both frees the ax25_dev and re-dereferences the dangling dev-\u003eax25_ptr. Although received AX.25 frames also read dev-\u003eax25_ptr in ax25_rcv(), an adjacent radio/L2 peer cannot itself cause the free, so the attacker must be local.\nAC:L - No race needs to be won: SO_BINDTODEVICE stores ax25-\u003eax25_dev without a reference while ax25_release() drops one, so a single setsockopt+close deterministically drives the refcount to zero and kfree()s the object still published in dev-\u003eax25_ptr. The pure device-down race variant is also attacker-driven by spinning setsockopt/connect in a loop.\nPR:L - ax25_create() imposes no capability check for SOCK_DGRAM/SOCK_SEQPACKET, and the AF_AX25 module autoloads via the net-pf-3 alias, so any unprivileged local user in the init namespace can reach every vulnerable path. Root is only needed for the one-time deployment setup of the AX.25 port, not by the attacker.\nUI:N - The entire sequence is performed by the attacker\u0027s own process through socket(), setsockopt(), connect()/sendmsg() and close(); no victim action is involved.\nS:U - The freed ax25_dev and the corrupted kernel heap are entirely within the kernel\u0027s own security authority, with no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - After the free, ax25_fillin_cb() copies bytes from the reclaimed slab object into the socket\u0027s t1/t2/t3/n2/paclen/window/backoff fields, which userspace reads back with getsockopt() \u2014 a direct kernel heap disclosure \u2014 and the general UAF read of ax25_dev-\u003edev/-\u003eforward enables broader information leakage.\nI:H - The dangling pointer yields repeated refcount_dec() and stores to ax25_dev-\u003eforward and -\u003edevice_up into memory that has been reallocated for other kernel objects, giving a controlled decrement/write primitive on a groomed heap that is exploitable for privilege escalation.\nA:H - Dereferencing and freeing the already-freed ax25_dev reliably produces a kernel oops/panic (and netdev refcount underflow), and the same commit fixes a genuine sk_lock-AF_AX25 versus rtnl_mutex ABBA deadlock that permanently wedges the rtnl mutex and with it the entire networking stack."
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              "url": "https://git.kernel.org/stable/c/2802ed4ced27ebd474828fc67ffd7d66f11e3605"
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        "assignerShortName": "Linux",
        "cveId": "CVE-2025-21812",
        "datePublished": "2025-02-27T20:01:02.837Z",
        "dateReserved": "2024-12-29T08:45:45.774Z",
        "dateUpdated": "2026-08-05T11:54:40.014Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.