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CVE Vulnerability Database
Vulnerability Database/CVE-2026-23055

CVE-2026-23055: Linux Kernel I2C Suspend Vulnerability

CVE-2026-23055 is a suspend handling flaw in the Linux kernel I2C RIIC driver that causes transfer attempts while suspended. This article covers the technical details, affected versions, system impact, and mitigation.

Updated: May 16, 2026

CVE-2026-23055 Overview

CVE-2026-23055 is a Linux kernel flaw in the Renesas i2c-riic driver. The issue stems from incorrect ordering of system sleep callbacks in the suspend/resume path. I2C transfers can still be attempted while the controller is already suspended, triggering a WARNING from __i2c_smbus_xfer and disrupting devices that depend on I2C during the suspend cycle, such as the isl1208 real-time clock on Renesas RZ/G3E platforms.

Critical Impact

Improper suspend ordering in the riic I2C driver causes transfers to be attempted on a suspended controller, producing kernel warnings and breaking dependent devices like RTCs during system sleep on Renesas RZ/G3E hardware.

Affected Products

  • Linux kernel i2c-riic driver (Renesas I2C controller)
  • Renesas RZ/G3E platforms (for example, SMARC EVK based on r9a09g047e57)
  • Kernel branches containing commit 53326135d0e0 ("i2c: riic: Add suspend/resume support")

Discovery Timeline

  • 2026-02-04 - CVE-2026-23055 published to NVD
  • 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2026-23055

Vulnerability Analysis

The i2c-riic driver registered its suspend and resume callbacks in the standard system sleep phase. After the controller was autosuspended through runtime power management, runtime PM was disabled in suspend_late(), leaving no path to wake the controller before the system entered the noirq phase.

During resume, the controller only became available again after resume_early() re-enabled runtime PM. Drivers depending on I2C during the late suspend or early resume window, such as the isl1208 RTC invoked from rtc_suspend(), attempted transfers against a suspended controller. The I2C core detected the violation in __i2c_smbus_xfer and emitted the "Transfer while suspended" warning at drivers/i2c/i2c-core.h:56.

The fix moves suspend handling to the NOIRQ phase. The suspend() callback now wakes the controller while runtime PM is still enabled, suspend_noirq() calls pm_runtime_force_suspend(), resume_noirq() calls pm_runtime_force_resume(), and the resume() callback re-enables autosuspend.

Root Cause

The root cause is inappropriate ordering of system sleep callbacks introduced by commit 53326135d0e0. Placing suspend logic in the standard phase rather than NOIRQ left a window where dependent kernel subsystems requested I2C transfers after the controller was already powered down.

Attack Vector

This is a local reliability and correctness defect triggered through normal system power transitions. No remote attack vector is documented. Exploitation in a security sense is not described in the upstream report; the impact is a kernel warning and broken functionality for I2C-attached devices during suspend and resume.

The vulnerability mechanism is described in prose because no verified exploit code is available. See the upstream commits for the patch implementation: Kernel Git Commit 0b4c0fb, Kernel Git Commit 469f8fe, and Kernel Git Commit e383f09.

Detection Methods for CVE-2026-23055

Indicators of Compromise

  • Kernel log entries containing the string Transfer while suspended originating from __i2c_smbus_xfer.
  • WARNING backtraces referencing drivers/i2c/i2c-core.h:56 during suspend or resume on Renesas RZ/G3E systems.
  • Failed RTC reads in the suspend path, such as isl1208_i2c_read_time invoked from rtc_suspend.

Detection Strategies

  • Audit dmesg and persistent kernel logs after suspend/resume cycles for the warning signature.
  • Confirm the running kernel includes commit 53326135d0e0 but lacks the NOIRQ fix commits referenced in the upstream patch series.
  • Verify driver pm_ops registration on riic devices to ensure NOIRQ callbacks are populated.

Monitoring Recommendations

  • Forward kernel ring buffer entries to a centralized log pipeline and alert on i2c-core warnings.
  • Track suspend/resume failure rates on fleets of Renesas-based embedded devices.
  • Include RTC drift or read failures in post-resume health checks.

How to Mitigate CVE-2026-23055

Immediate Actions Required

  • Apply the upstream Linux kernel patch series that relocates riic suspend handling to the NOIRQ phase.
  • Rebuild and deploy kernels for affected Renesas RZ/G3E devices.
  • Validate suspend and resume on representative hardware after patching.

Patch Information

The fix is delivered through the following upstream commits: Kernel Git Commit 0b4c0fb, Kernel Git Commit 469f8fe, and Kernel Git Commit e383f09. The change moves suspend handling so pm_runtime_force_suspend() runs in suspend_noirq() and pm_runtime_force_resume() runs in resume_noirq(), keeping the controller available for late-suspending and early-resuming devices.

Workarounds

  • Disable runtime PM autosuspend for the riic controller on affected boards until the patch is applied.
  • Remove or defer I2C-dependent suspend operations, such as RTC reads, where operationally acceptable.
  • Pin affected systems to a kernel version prior to commit 53326135d0e0 if patching is not yet possible.

Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.

  • Vulnerability Details
  • TypeOther

  • Vendor/TechLinux Kernel

  • SeverityNONE

  • CVSS ScoreN/A

  • EPSS Probability0.03%

  • Known ExploitedNo
  • Impact Assessment
  • ConfidentialityNone
  • IntegrityNone
  • AvailabilityNone
  • Technical References
  • Kernel Git Commit 0b4c0fb

  • Kernel Git Commit 469f8fe

  • Kernel Git Commit e383f09
  • Related CVEs
  • CVE-2026-46265: Linux Kernel RDMA WQ_MEM_RECLAIM Warning

  • CVE-2026-46257: Linux Kernel SP804 Timer Oops Vulnerability

  • CVE-2026-46255: Linux Kernel EDMA Clock Disable Bug

  • CVE-2026-46239: Linux Kernel OV5647 PM Refcount Leak
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