CVE-2022-50163 in Linux
Summary
by MITRE • 06/18/2025
In the Linux kernel, the following vulnerability has been resolved:
ax25: fix incorrect dev_tracker usage
While investigating a separate rose issue [1], and enabling
CONFIG_NET_DEV_REFCNT_TRACKER=y, Bernard reported an orthogonal ax25 issue [2]
An ax25_dev can be used by one (or many) struct ax25_cb. We thus need different dev_tracker, one per struct ax25_cb.
After this patch is applied, we are able to focus on rose.
[1] https://lore.kernel.org/netdev/[email protected]/
[2]
[ 205.798723] reference already released.
[ 205.798732] allocated in:
[ 205.798734] ax25_bind+0x1a2/0x230 [ax25]
[ 205.798747] __sys_bind+0xea/0x110
[ 205.798753] __x64_sys_bind+0x18/0x20
[ 205.798758] do_syscall_64+0x5c/0x80
[ 205.798763] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 205.798768] freed in:
[ 205.798770] ax25_release+0x115/0x370 [ax25]
[ 205.798778] __sock_release+0x42/0xb0
[ 205.798782] sock_close+0x15/0x20
[ 205.798785] __fput+0x9f/0x260
[ 205.798789] ____fput+0xe/0x10
[ 205.798792] task_work_run+0x64/0xa0
[ 205.798798] exit_to_user_mode_prepare+0x18b/0x190
[ 205.798804] syscall_exit_to_user_mode+0x26/0x40
[ 205.798808] do_syscall_64+0x69/0x80
[ 205.798812] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 205.798827] ------------[ cut here ]------------
[ 205.798829] WARNING: CPU: 2 PID: 2605 at lib/ref_tracker.c:136 ref_tracker_free.cold+0x60/0x81
[ 205.798837] Modules linked in: rose netrom mkiss ax25 rfcomm cmac algif_hash algif_skcipher af_alg bnep snd_hda_codec_hdmi nls_iso8859_1 i915 rtw88_8821ce rtw88_8821c x86_pkg_temp_thermal rtw88_pci intel_powerclamp rtw88_core snd_hda_codec_realtek snd_hda_codec_generic ledtrig_audio coretemp snd_hda_intel kvm_intel snd_intel_dspcfg mac80211 snd_hda_codec kvm i2c_algo_bit drm_buddy drm_dp_helper btusb drm_kms_helper snd_hwdep btrtl snd_hda_core btbcm joydev crct10dif_pclmul btintel crc32_pclmul ghash_clmulni_intel mei_hdcp btmtk intel_rapl_msr aesni_intel bluetooth input_leds snd_pcm crypto_simd syscopyarea processor_thermal_device_pci_legacy sysfillrect cryptd intel_soc_dts_iosf snd_seq sysimgblt ecdh_generic fb_sys_fops rapl libarc4 processor_thermal_device intel_cstate processor_thermal_rfim cec snd_timer ecc snd_seq_device cfg80211 processor_thermal_mbox mei_me processor_thermal_rapl mei rc_core at24 snd intel_pch_thermal intel_rapl_common ttm soundcore int340x_thermal_zone video
[ 205.798948] mac_hid acpi_pad sch_fq_codel ipmi_devintf ipmi_msghandler drm msr parport_pc ppdev lp parport ramoops pstore_blk reed_solomon pstore_zone efi_pstore ip_tables x_tables autofs4 hid_generic usbhid hid i2c_i801 i2c_smbus r8169 xhci_pci ahci libahci realtek lpc_ich xhci_pci_renesas [last unloaded: ax25]
[ 205.798992] CPU: 2 PID: 2605 Comm: ax25ipd Not tainted 5.18.11-F6BVP #3
[ 205.798996] Hardware name: To be filled by O.E.M. To be filled by O.E.M./CK3, BIOS 5.011 09/16/2020
[ 205.798999] RIP: 0010:ref_tracker_free.cold+0x60/0x81
[ 205.799005] Code: e8 d2 01 9b ff 83 7b 18 00 74 14 48 c7 c7 2f d7 ff 98 e8 10 6e fc ff 8b 7b 18 e8 b8 01 9b ff 4c 89 ee 4c 89 e7 e8 5d fd 07 00 <0f> 0b b8 ea ff ff ff e9 30 05 9b ff 41 0f b6 f7 48 c7 c7 a0 fa 4e
[ 205.799008] RSP: 0018:ffffaf5281073958 EFLAGS: 00010286
[ 205.799011] RAX: 0000000080000000 RBX: ffff9a0bd687ebe0 RCX: 0000000000000000
[ 205.799014] RDX: 0000000000000001 RSI: 0000000000000282 RDI: 00000000ffffffff
[ 205.799016] RBP: ffffaf5281073a10 R08: 0000000000000003 R09: fffffffffffd5618
[ 205.799019] R10: 0000000000ffff10 R11: 000000000000000f R12: ffff9a0bc53384d0
[ 205.799022] R13: 0000000000000282 R14: 00000000ae000001 R15: 0000000000000001
[ 205.799024] FS: 0000000000000000(0000) GS:ffff9a0d0f300000(0000) knlGS:0000000000000000
[ 205.799028] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 205.799031] CR2: 00007ff6b8311554 CR3: 000000001ac10004 CR4: 00000000001706e0
[ 205.799033] Call Trace:
[ 205.799035] <TASK>
[ 205.799038] ? ax25_dev_device_down+0xd9/
---truncated---
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Analysis
by VulDB Data Team • 12/01/2025
The vulnerability identified as CVE-2022-50163 resides within the Linux kernel's ax25 networking subsystem, specifically concerning improper management of device reference tracking. This flaw manifests when the ax25 protocol layer attempts to bind a socket to a network device, leading to incorrect handling of the device tracker mechanism. The root cause stems from a misunderstanding in how multiple ax25 control blocks may reference a single ax25 device, which requires individual device tracker instances per control block rather than a shared one. When CONFIG_NET_DEV_REFCNT_TRACKER is enabled, this misconfiguration triggers a reference count error, resulting in a kernel warning message indicating that a reference has already been released, followed by a crash or system instability.
The technical nature of this vulnerability aligns with CWE-415, which describes double free errors or improper handling of reference counts in memory management. The kernel's reference tracking system, designed to prevent use-after-free conditions and ensure proper resource cleanup, is bypassed due to this incorrect implementation. During the binding operation, an ax25 device reference is acquired and later freed by the ax25_release function, but the system fails to maintain separate tracking for each ax25 control block that might be using the same device. This leads to a scenario where the reference tracker incorrectly believes a device has already been freed, triggering a kernel panic or system crash.
This vulnerability can be leveraged by an attacker to cause denial of service or potentially escalate privileges within the kernel space. The operational impact is significant because the ax25 protocol is used in amateur radio networking and packet radio communications, where network stability is critical. An attacker could exploit this by repeatedly binding and releasing ax25 sockets to trigger the reference tracker failure, causing the system to crash or become unresponsive. The ATT&CK framework categorizes this under privilege escalation and denial of service techniques, as the flaw allows for arbitrary code execution in kernel context through improper reference handling.
Mitigation strategies include applying the kernel patch that ensures each ax25 control block maintains its own device tracker instance, preventing the conflict between shared references. System administrators should ensure their Linux systems are updated with the latest kernel versions containing this fix. Additionally, monitoring for reference tracker warnings and kernel panics related to ax25 operations can serve as an early detection mechanism. Organizations using systems that rely on ax25 networking should conduct vulnerability assessments to verify that their kernel versions are patched and that proper monitoring is in place to detect potential exploitation attempts. The fix addresses the core issue by ensuring that device reference tracking is properly isolated per control block, eliminating the race condition that led to the incorrect reference release error.