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PatchSiren cyber security CVE debrief

CVE-2026-64213 Linux CVE debrief

A concurrency issue in the Linux kernel's hwmon lm90 driver can cause an interrupt storm when an alert interrupt occurs concurrently with a sysfs write operation. This issue arises because lm90_alert() executes in the smbus alert context and calls lm90_update_confreg() to disable the hardware alert line without acquiring hwmon_lock. Concurrently, sysfs write operations hold hwmon_lock, temporarily modify data->config, and then restore it. If an alert interrupt occurs concurrently with a sysfs write, the sysfs path overwrites the alert handler's modifications to data->config and the hardware register, unintentionally re-enabling the hardware alert line while the alarm is still active. This can lead to system instability and potential security risks if not addressed. Linux system administrators and users, especially those with systems using the lm90 driver, should be aware of this issue and apply the necessary patches to prevent potential interrupt storms and system instability. The official patches should be applied to update the lm90 driver and ensure proper locking to prevent interrupt storms.

Vendor
Linux
Product
Unknown
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-24
Original CVE updated
2026-08-11
Advisory published
2026-07-24
Advisory updated
2026-08-11

Who should care

Linux system administrators and users, especially those with systems using the lm90 driver, should be aware of this issue and apply the necessary patches to prevent potential interrupt storms and system instability.

Technical summary

The Linux kernel's hwmon lm90 driver has a concurrency issue. lm90_alert() executes in the smbus alert context and calls lm90_update_confreg() to disable the hardware alert line without acquiring hwmon_lock. Concurrent sysfs write operations hold hwmon_lock, modify data->config, and then restore it. If an alert interrupt occurs concurrently with a sysfs write, the sysfs path overwrites the alert handler's modifications to data->config and the hardware register, causing an interrupt storm.

Defensive priority

Apply the official patches to update the lm90 driver and ensure proper locking to prevent interrupt storms.

Recommended defensive actions

  • Apply patches from https://git.kernel.org/stable/c/873e919e3101063a7a75989510ccfc125a4391cf
  • Apply patches from https://git.kernel.org/stable/c/b0b66aae8a94c3663d47e4000b0e81b89ce32186
  • Apply patches from https://git.kernel.org/stable/c/bed1fc32e0eb653806fa98afcf55f9a311fc4ce2
  • Inventory Linux systems for lm90 driver usage and ensure patch deployment
  • Monitor for unusual interrupt activity on systems with lm90 driver

Evidence notes

The issue arises from lm90_alert() executing in the smbus alert context and calling lm90_update_confreg() to disable the hardware alert line without acquiring hwmon_lock. Concurrent sysfs write operations hold hwmon_lock, modify data->config, and then restore it. If an alert interrupt occurs concurrently with a sysfs write, the sysfs path overwrites the alert handler's modifications to data->config and the hardware register, unintentionally re-enabling the hardware alert line while the alarm is still active.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-24T16:16:48.950Z and has not been modified since then. The NVD entry is currently Analyzed.