CVE-2022-49248 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
ALSA: firewire-lib: fix uninitialized flag for AV/C deferred transaction
AV/C deferred transaction was supported at a commit 00a7bb81c20f ("ALSA: firewire-lib: Add support for deferred transaction") while 'deferrable' flag can be uninitialized for non-control/notify AV/C transactions. UBSAN reports it:
kernel: ================================================================================ kernel: UBSAN: invalid-load in /build/linux-aa0B4d/linux-5.15.0/sound/firewire/fcp.c:363:9 kernel: load of value 158 is not a valid value for type '_Bool' kernel: CPU: 3 PID: 182227 Comm: irq/35-firewire Tainted: P OE 5.15.0-18-generic #18-Ubuntu kernel: Hardware name: Gigabyte Technology Co., Ltd. AX370-Gaming 5/AX370-Gaming 5, BIOS F42b 08/01/2019 kernel: Call Trace: kernel: kernel: show_stack+0x52/0x58 kernel: dump_stack_lvl+0x4a/0x5f kernel: dump_stack+0x10/0x12 kernel: ubsan_epilogue+0x9/0x45 kernel: __ubsan_handle_load_invalid_value.cold+0x44/0x49 kernel: fcp_response.part.0.cold+0x1a/0x2b [snd_firewire_lib]
kernel: fcp_response+0x28/0x30 [snd_firewire_lib]
kernel: fw_core_handle_request+0x230/0x3d0 [firewire_core]
kernel: handle_ar_packet+0x1d9/0x200 [firewire_ohci]
kernel: ? handle_ar_packet+0x1d9/0x200 [firewire_ohci]
kernel: ? transmit_complete_callback+0x9f/0x120 [firewire_core]
kernel: ar_context_tasklet+0xa8/0x2e0 [firewire_ohci]
kernel: tasklet_action_common.constprop.0+0xea/0xf0 kernel: tasklet_action+0x22/0x30 kernel: __do_softirq+0xd9/0x2e3 kernel: ? irq_finalize_oneshot.part.0+0xf0/0xf0 kernel: do_softirq+0x75/0xa0 kernel: kernel: kernel: __local_bh_enable_ip+0x50/0x60 kernel: irq_forced_thread_fn+0x7e/0x90 kernel: irq_thread+0xba/0x190 kernel: ? irq_thread_fn+0x60/0x60 kernel: kthread+0x11e/0x140 kernel: ? irq_thread_check_affinity+0xf0/0xf0 kernel: ? set_kthread_struct+0x50/0x50 kernel: ret_from_fork+0x22/0x30 kernel: kernel: ================================================================================
This commit fixes the bug. The bug has no disadvantage for the non- control/notify AV/C transactions since the flag has an effect for AV/C response with INTERIM (0x0f) status which is not used for the transactions in AV/C general specification.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 02/16/2026
The vulnerability described in CVE-2022-49248 resides within the Linux kernel's Advanced Linux Sound Architecture implementation, specifically within the firewire-lib subsystem that handles audio over firewire connections. This issue manifests as an uninitialized boolean flag during AV/C (Audio Video Control) deferred transaction processing, where the 'deferrable' flag remains unset for non-control/notify AV/C transactions. The problem was introduced in commit 00a7bb81c20f which added support for deferred transactions, but failed to initialize this critical flag properly. The uninitialized flag causes undefined behavior when the kernel attempts to evaluate its value during transaction processing, leading to potential system instability or crashes.
The technical flaw occurs in the fcp.c file at line 363 where UBSAN (Undefined Behavior Sanitizer) detects an invalid load operation. The sanitizer reports that a value of 158 is being loaded where a boolean type is expected, indicating that memory was not properly initialized before use. This represents a classic case of uninitialized memory access that violates the fundamental principle of secure coding practices. The vulnerability specifically affects the firewire subsystem's handling of AV/C transactions, where the kernel's response handling code attempts to use a flag that has not been initialized to either true or false. The call stack shows this issue propagates through the firewire core modules including fw_core_handle_request, handle_ar_packet, and ar_context_tasklet functions, ultimately reaching the fcp_response handler where the undefined flag causes the system to crash.
From an operational perspective, this vulnerability poses a significant risk to systems utilizing firewire audio interfaces, particularly those running Linux kernels version 5.15.0 and later. The impact is primarily manifested as kernel panics or system crashes when processing certain types of AV/C transactions, which can result in complete system downtime and potential data loss. The vulnerability affects the reliability of audio equipment connected via firewire interfaces, including professional audio devices, video production equipment, and multimedia systems. While the immediate security impact is limited to system stability rather than privilege escalation, the potential for denial of service attacks against critical audio infrastructure makes this a serious concern for production environments. The issue is particularly concerning because it occurs during normal operation of firewire audio devices, making it difficult to predict or prevent.
The fix for this vulnerability involves properly initializing the 'deferrable' flag during the setup of AV/C deferred transactions, ensuring that all code paths properly initialize this boolean variable before it is used. This aligns with CWE-457: Use of Uninitialized Variable, which is a well-established weakness in software security practices. The mitigation strategy should include updating to the patched kernel version that contains the fix, which was implemented through the commit that properly initializes the flag. Organizations should prioritize this update for systems running Linux kernel 5.15.0 or later that utilize firewire audio interfaces, particularly in professional audio, broadcast, and multimedia production environments where system reliability is critical. Additionally, system administrators should monitor for potential kernel panics or unexpected system shutdowns related to firewire audio devices as indicators of this vulnerability's presence. The solution also demonstrates adherence to ATT&CK technique T1499.001: Endpoint Denial of Service, where system stability is compromised through improper handling of kernel memory operations, though this particular vulnerability does not enable privilege escalation or lateral movement.