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CVE-2026-74738— regmap: sdw-mbq: don't call an unset readable_reg callback

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： regmap: sdw-mbq: 不要调用未设置的 readable_reg 回调 通过调用 来决定是否轮询 Function Busy 位。该函数是 的直接副本。但此回调是可选的： 将 NULL 的 视为“所有寄存器均可读”，许多驱动都依赖这一行为。例如， 和 在创建 MBQ regmap 时均未设置该回调。 自提交 （“regmap: sdw-mbq: 允许对可延时的控制进行延迟处理”）之后，轮询逻辑会在每次 时触发，而不再仅限于驱动标记为可延时的控制项。因此，若这

AI Predicted 7.2 Difficulty: Hard EPSS 0.17% · P7

Possible ATT&CK Techniques 1 AI

T1218 · System Binary Proxy Execution

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux 5bc493bf0c37c157bf2eb364e55a1c6f8bc43a69< 6cf600b276a55a6481462830607a611f32e737c0 affected
5bc493bf0c37c157bf2eb364e55a1c6f8bc43a69< 5bd8e897ecf558507142f4553e4526adfc1d6482 affected
5bc493bf0c37c157bf2eb364e55a1c6f8bc43a69< 00268f9452d2a0d660aa9c1bb0ca07a994af6a4f affected
6.14 affected
< 6.14 unaffected
6.18.46≤ 6.18.* unaffected
7.1.10≤ 7.1.* unaffected
7.2≤ * unaffected
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I. Basic Information for CVE-2026-74738

Vulnerability Information
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Vulnerability Title
regmap: sdw-mbq: don't call an unset readable_reg callback
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 5bc493bf0c37c157bf2eb364e55a1c6f8bc43a69 ~ 6cf600b276a55a6481462830607a611f32e737c0 -
Linux Linux 6.14 -

II. Public POCs for CVE-2026-74738

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III. Intelligence Information for CVE-2026-74738

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Patches & Fixes for CVE-2026-74738 (3)

Same Patch Batch · Linux · 2026-08-26 · 92 CVEs total

CVE-2026-80558 9.8 CRITICAL libceph: Avoid using invalid osd indices from primary_temp
CVE-2026-80587 9.8 CRITICAL mptcp: avoid combining some incoming suboptions
CVE-2026-74752 9.8 CRITICAL sctp: validate cookie AUTH state before use
CVE-2026-74746 9.8 CRITICAL netfilter: flowtable: publish GC-visible tuple last
CVE-2026-80519 9.8 CRITICAL ovpn: finish crypto callback cleanup before peer release
CVE-2026-74744 9.8 CRITICAL ipvlan: inherit needed_headroom and needed_tailroom from phy_dev
CVE-2026-74743 9.8 CRITICAL macvlan: inherit needed_headroom and needed_tailroom from lowerdev
CVE-2026-80557 9.8 CRITICAL libceph: fix OOB read in decode_watchers() via missing bounds check
CVE-2026-80586 9.8 CRITICAL mptcp: options: reset DSS fields in case of unexpected size
CVE-2026-80589 9.8 CRITICAL block: stop the timeout timer when releasing a never added disk
CVE-2026-80561 9.8 CRITICAL libceph: fix multiple unsafe decodes in decode_locker()
CVE-2026-74737 9.8 CRITICAL net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG
CVE-2026-80528 9.8 CRITICAL ceph: avoid fs reclaim while using current->journal_info
CVE-2026-80585 9.4 CRITICAL mptcp: fastopen: only mark MPTFO subflows with SYN data
CVE-2026-74751 9.4 CRITICAL riscv: lib: Fix ZBB strnlen reading past count boundary
CVE-2026-80554 9.3 CRITICAL s390/vfio_ccw: Limit the number of channel program segments
CVE-2026-80551 9.3 CRITICAL s390/vfio_ccw: Ensure first IDAW remains constant
CVE-2026-80576 8.8 HIGH drm/amdgpu: reject oversized IBs with per-ring packet limits
CVE-2026-80547 8.8 HIGH s390/vfio_ccw: Implement a crw lock
CVE-2026-80548 8.8 HIGH s390/vfio_ccw: Selectively expand io_mutex

Showing top 20 of 92 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-74738

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