CVE-2026-74549 hwmon: (nct6775-core) Prevent access to unsupported weight registers
A Linux kernel driver bug allows out-of-bounds reads leading to invalid hardware access, potentially causing system crashes or misconfiguration.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74549?
CVE-2026-74549 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (nct6775-core) Prevent access to unsupported weight registers
Sashiko reports:
During initialization of the nct6116 chip, the driver sets data->pwm_num to 5. However, it assigns several NCT6106 register arrays (such as NCT6106_REG_WEIGHT_DUTY_STEP, NCT6106_REG_WEIGHT_TEMP_SEL, and NCT6106_REG_WEIGHT_TEMP_*) to data->REG_PWM and data->REG_WEIGHT_TEMP. These arrays only contain 3 elements.
In nct6775_update_pwm(), the driver iterates up to data->pwm_num. If data->has_pwm has bits 3 or 4 set (which is structurally possible for nct6116), the loop attempts to read elements at index 3 and 4 from these 3-element arrays. This results in a global out-of-bounds read, which can be caught by KASAN.
Furthermore, the driver uses these garbage out-of-bounds values as hardware register addresses for subsequent read and write operations. This leads to invalid hardware register access, potentially causing hardware misconfiguration or system crashes.
The underlying problem is that the chip does support up to five fan control channels, but only the first three support weight control. Fix the problem by extending the affected weight register arrays with zeroed fields. The driver uses zeroed register addresses to determine if a register is supported or not, and skips accesses for unsupported registers.
Which versions are affected by CVE-2026-74549?
How do I fix CVE-2026-74549?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-74549 being exploited?
There is no known exploitation of CVE-2026-74549 in the wild and no public exploit code.
Sources
Also known as AZL-96561, BELL-CVE-2026-74549, DEBIAN-CVE-2026-74549, GHSA-8cf5-68w2-4vhx, UBUNTU-CVE-2026-74549.