mfd: qnap-mcu: keep the reply buffer alive past a command timeout

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80975
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:03 UTC
Updated2026-09-13 07:17:04 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: mfd: qnap-mcu: keep the reply buffer alive past a command timeout qnap_mcu_exec() publishes an on-stack buffer to the receive path: unsigned char rx[QNAP_MCU_RX_BUFFER_SIZE]; ... reply->data = rx; reply->length = length; and qnap_mcu_receive_buf() writes into it from the serdev receive path, which runs out of flush_to_ldisc() and is not serialized against qnap_mcu_exec() at all. bus_lock cannot cover it, because qnap_mcu_exec() holds that mutex across wait_for_completion_timeout(). On a timeout qnap_mcu_exec() returns with reply->data still pointing at its own frame. A reply that arrives late, or an unsolicited message from the MCU, is then written into a stack frame that has been left, corrupting whatever runs next on that stack. The same applies when qnap_mcu_write() fails, since that path returns without touching the reply state either. Move the receive buffer into struct qnap_mcu. It is 37 bytes and the structure is devm_kzalloc()ed, so it lives as long as the driver, and a late write lands in memory that is still valid and is reinitialized by the next command. bus_lock keeps commands from sharing it. This deliberately does not clear reply->data or reply->length on the timeout path. Doing so races with qnap_mcu_receive_buf(), which reads both after its if (!reply->length) return size; check: clearing reply->data gives a NULL dereference, and clearing reply->length alone removes the reply->received == reply->length exit condition, so the copy loop runs until the uart chunk is consumed and overruns the buffer. Leaving both set keeps the write bounded by reply->length, which qnap_mcu_exec() has already checked against sizeof(mcu->rx).

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001610000 probability, percentile 0.056820000 (date 2026-09-14)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 998f70d1806bb718a7565f350283e4a79c8cbb4b 0b6680e306397097a97767447368221fac753809 git Not specified
CNA Linux Linux affected 998f70d1806bb718a7565f350283e4a79c8cbb4b 8391ee06d08845a0a165b5fe679ba326915166b2 git Not specified
CNA Linux Linux affected 998f70d1806bb718a7565f350283e4a79c8cbb4b 47504742cea7878ebd1bf1491bbed923df6b90b1 git Not specified
CNA Linux Linux affected 6.14 Not specified
CNA Linux Linux unaffected 6.14 semver Not specified
CNA Linux Linux unaffected 6.18.51 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/8391ee06d08845a0a165b5fe679ba326915166b2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0b6680e306397097a97767447368221fac753809 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/47504742cea7878ebd1bf1491bbed923df6b90b1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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