# CVE-2026-74738: linux: In the Linux kernel, the following vulnerability has been resolved:  regmap: sdw-mbq: don't call an unset readable_re...

CVE-2026-74738 is fixed in linux on 1 platform by DEBIAN-CVE-2026-74738 (version 7.1.10-1), released September 4, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-74738
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 26, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.1.10-1 | [DEBIAN-CVE-2026-74738](https://patchblox.com/security/data/fix/linux/debian-cve-2026-74738.md) | Sep 4, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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