CVE-2026-97515
Received Received - Intake

Linux Kernel I3C IRQ Storm on NPCM845

Publication date: 2026-09-24

Last updated on: 2026-09-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: i3c: master: svc: Prevent IRQ storm from false SLVSTART on NPCM845 On NPCM845, when a target on the I3C bus gets stuck holding SDA low, the controller reports a false Master Request (MR) in-band interrupt event. The driver handles this by emitting a STOP condition to restore the bus. However, the hardware quirk SVC_I3C_QUIRK_FALSE_SLVSTART indicates that emitting a STOP condition may spuriously set the SLVSTART interrupt status bit. In the Master Request case, this creates a feedback loop: the STOP triggers a new SLVSTART event, the IRQ handler fires again, the controller still reports an MR type, another STOP is emitted, and the cycle repeats indefinitely, resulting in an IRQ storm that can lock up the CPU. Clear the SLVSTART status bit explicitly after emitting the STOP in the Master Request IBI handler when the SVC_I3C_QUIRK_FALSE_SLVSTART quirk is set. This breaks the feedback loop without affecting normal SLVSTART processing, which is already guarded in the top-level IRQ handler by checking that MSTATUS is in SLVREQ state.

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Meta Information

Published
2026-09-24
Last Modified
2026-09-24
Generated
2026-09-24
AI Q&A
2026-09-24
EPSS Evaluated
N/A
NVD
CVE-2026-97515
EUVD
EUVD-2026-86113

Affected Vendors & Products

Currently, no data is known.

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability affects the Linux kernel's I3C bus controller driver on NPCM845 systems. When a device on the I3C bus gets stuck holding the SDA line low, the controller falsely reports a Master Request interrupt. The driver attempts to fix this by sending a STOP condition, but a hardware quirk causes the SLVSTART interrupt status bit to be set again, creating an infinite loop of interrupts that locks up the CPU.

Detection Guidance

This vulnerability is specific to Linux kernel I3C bus handling on NPCM845 hardware. Detection requires checking kernel logs for repeated SLVSTART interrupts or IRQ storms on the I3C bus. Monitor dmesg or /var/log/kern.log for messages indicating I3C controller issues or IRQ flooding.

Impact Analysis

This vulnerability can cause system instability by triggering an interrupt storm that consumes CPU resources indefinitely. This may lead to system freezes, unresponsiveness, or crashes, particularly on systems using NPCM845 with I3C bus devices.

Mitigation Strategies

Apply the Linux kernel patch that clears the SLVSTART status bit after STOP emission in the Master Request IBI handler. Update to a kernel version containing the fix for CVE-2026-97515. If immediate patching is not possible, disable I3C bus operations on NPCM845 systems until the update is applied.

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