CVE-2025-21847 in Linux
Summary
by MITRE • 03/12/2025
In the Linux kernel, the following vulnerability has been resolved:
ASoC: SOF: stream-ipc: Check for cstream nullity in sof_ipc_msg_data()
The nullity of sps->cstream should be checked similarly as it is done in sof_set_stream_data_offset() function. Assuming that it is not NULL if sps->stream is NULL is incorrect and can lead to NULL pointer dereference.
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Analysis
by VulDB Data Team • 06/02/2026
The vulnerability identified as CVE-2025-21847 resides within the Linux kernel's Sound Open Firmware (SOF) subsystem, specifically in the stream inter-process communication handling mechanism. This issue affects the Advanced SoC (ASoC) framework's SOF implementation where audio stream management occurs through inter-process communication channels. The flaw manifests in the sof_ipc_msg_data() function which processes audio stream data messages between kernel components and firmware. The vulnerability represents a classic null pointer dereference scenario that can lead to system instability and potential privilege escalation.
The technical root cause stems from inadequate null pointer validation within the SOF audio subsystem's stream processing logic. During audio stream initialization and data handling, the code assumes that if sps->stream is NULL, then sps->cstream must necessarily contain valid data. This assumption is fundamentally flawed because the cstream pointer can independently be NULL even when stream is NULL, creating a dangerous condition where dereferencing cstream leads to kernel memory corruption. The vulnerability is particularly concerning as it occurs in a critical path of audio processing where the kernel handles data flow between userspace applications and hardware audio interfaces. This flaw aligns with CWE-476 which identifies null pointer dereference as a common security weakness, and specifically relates to improper handling of null references in kernel space code.
The operational impact of this vulnerability extends beyond simple system crashes, potentially enabling malicious actors to exploit the null pointer dereference for privilege escalation or denial of service attacks. When an attacker can trigger the condition where sps->cstream is NULL but the code attempts to access it, the kernel may crash or exhibit undefined behavior, leading to system instability. In environments where audio processing is critical, such as servers or embedded systems, this vulnerability could be leveraged to disrupt audio services or potentially gain elevated privileges within the kernel space. The attack surface is particularly relevant in multimedia applications, real-time audio processing systems, and embedded devices that rely heavily on SOF for audio functionality. This vulnerability demonstrates the importance of proper null pointer validation in kernel code as outlined in the ATT&CK framework's kernel-mode rootkit techniques that often exploit similar memory management flaws.
The mitigation strategy for CVE-2025-21847 involves implementing proper null pointer checks in the sof_ipc_msg_data() function, specifically ensuring that sps->cstream is validated before any dereference operations occur. The fix should mirror the existing pattern used in sof_set_stream_data_offset() function where nullity checks are properly implemented. Kernel maintainers should enforce comprehensive validation of all stream pointers before data processing, implementing defensive programming practices that prevent assumptions about pointer states. This includes adding explicit null checks and proper error handling that returns appropriate error codes rather than attempting to dereference potentially invalid pointers. System administrators should ensure immediate deployment of kernel updates containing the patched code and monitor for any unusual system behavior that might indicate exploitation attempts. The fix should also include enhanced logging of stream processing operations to facilitate detection of potential exploitation attempts and aid in forensic analysis.