CVE-2026-74738
Description
A flaw was found in the regmap: sdw-mbq component of the Linux kernel. This vulnerability occurs when the regmap_sdw_mbq_poll_busy() function attempts to call an unset readable_reg callback. If a device responds with COMMAND_IGNORED, it can lead to a NULL function pointer dereference. This could potentially result in a system crash or denial of service.
Statement
A Moderate-impact NULL function pointer dereference flaw was found in the Linux kernel's SoundWire MBQ (sdw-mbq) regmap support. The regmap_sdw_mbq_poll_busy() function decides whether to poll the Function Busy bit by calling the optional readable_reg callback, which drivers such as es9356 and tac5xx2-sdw may leave unset when building an MBQ regmap. Because the poll path now runs on every -ENODATA response, a device that answers COMMAND_IGNORED drives the kernel through a NULL function pointer, causing a kernel panic and a local denial of service. Only system availability is affected; there is no impact on confidentiality or integrity. Red Hat Product Security rated this flaw Moderate severity (CVSS 3.1 score 5.5, AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) because exploitation requires local access and specific SoundWire hardware. This flaw affects the kernel and kernel-rt components in Red Hat Enterprise Linux 9 (rhel-9.8.z, rhel-9.9, rhel-9.10), Red Hat Enterprise Linux 10 (rhel-10.2.z, rhel-10.3, rhel-10.4), and Red Hat In-Vehicle OS 2 (kernel and kernel-ivos-qualcomm components). Red Hat Enterprise Linux 6, 7, and 8, and the rhel-9.2.0.z, rhel-9.4.z, rhel-9.6.z, and rhel-10.0.z streams are not affected because the vulnerable code is not present in those kernels. For the affected streams the fix has been deferred to a future update because the issue is a local, availability-only denial of service that requires specific SoundWire hardware to trigger; the residual risk of deferral is a potential kernel panic on systems using affected devices such as the es9356 or tac5xx2-sdw codecs.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart
NULL pointer dereferences usually result in the failure of the process unless exception handling (on some platforms) is available and implemented. Even when exception handling is being used, it can still be very difficult to return the software to a safe state of operation.
Integrity,Confidentiality
Technical Impact: Execute Unauthorized Code or Commands; Read Memory; Modify Memory
In rare circumstances, when NULL is equivalent to the 0x0 memory address and privileged code can access it, then writing or reading memory is possible, which may lead to code execution.
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