regmap: sdw-mbq: don't call an unset readable_reg callback (CVE-2026-74738) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-74738

regmap: sdw-mbq: don't call an unset readable_reg callback

Answer in brief

CVE-2026-74738 records a Unknown severity vulnerability in regmap: sdw-mbq: don't call an unset readable_reg callback. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 26, 2026Updated Aug 26, 2026Source checked Aug 26, 2026First seen by HOL Aug 26, 2026Material review Aug 26, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=5bc493bf0c37c157bf2eb364e55a1c6f8bc43a69 <6cf600b276a55a6481462830607a611f32e737c0 \|\| >=5bc493bf0c37c157bf2eb364e55a1c6f8bc43a69 <5bd8e897ecf558507142f4553e4526adfc1d6482 \|\| >=5bc493bf0c37c157bf2eb364e55a1c6f8bc43a69 <00268f9452d2a0d660aa9c1bb0ca07a994af6a4f	6cf600b276a55a6481462830607a611f32e737c0, 5bd8e897ecf558507142f4553e4526adfc1d6482, 00268f9452d2a0d660aa9c1bb0ca07a994af6a4f
Linux/Linuxgeneric	6.14	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 6cf600b276a55a6481462830607a611f32e737c0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 26, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: regmap: sdw-mbq: don't call an unset readable_reg callback regmap_sdw_mbq_poll_busy() decides whether to poll the Function Busy bit by calling ctx->readable_reg(), which is a straight copy of config->readable_reg. That callback is optional: regmap_readable() treats a NULL ->readable_reg as "every register is readable", and drivers rely on that. es9356 and tac5xx2-sdw both build an MBQ regmap without one. Since commit ca1b11b36d82 ("regmap: sdw-mbq: Allow defers on undeferrable controls") the poll runs on every -ENODATA, not only for Controls the driver marked deferrable, so any of those devices answering COMMAND_IGNORED takes the kernel through a NULL function pointer. Treat a missing callback the way the rest of regmap does and poll.

Quoted source text, attributed separately from HOL analysis.