CVE-2026-64497 Overview
CVE-2026-64497 is a sign-extension defect in the Linux kernel iio/chemical/scd30 driver, which supports Sensirion SCD30 CO2 sensors. The flaw resides in the driver's handling of IEEE 754 float32 values received from the sensor. During conversion, the code applied a bitwise AND with ~BIT(31), which on 64-bit platforms expands to 0xFFFFFFFF7FFFFFFF due to implicit sign extension. This mask corrupts the exponent field of the float, producing incorrect sensor readings. The upstream fix refactors the initialization logic, introduces FIELD_GET() macros from linux/bitfield.h, and separates mantissa, exponent, and sign handling.
Critical Impact
Corruption of float32 exponent values returned by the SCD30 sensor driver, resulting in incorrect chemical measurement data delivered to userspace consumers.
Affected Products
- Linux kernel iio/chemical/scd30 driver
- Multiple stable kernel branches referenced in upstream commits
- Systems using Sensirion SCD30 CO2 sensors via industrial I/O subsystem
Discovery Timeline
- 2026-07-25 - CVE-2026-64497 published to NVD
- 2026-07-25 - Last updated in NVD database
Technical Details for CVE-2026-64497
Vulnerability Analysis
The scd30 driver reads IEEE 754 single-precision floats from the sensor and decomposes them into sign, exponent, and mantissa components. The pre-patch implementation combined variable declarations and initializations across multiple comma-separated lines, obscuring an incorrect bitmask operation. When the driver attempted to clear the sign bit using ~BIT(31), the expression evaluated as an unsigned long on 64-bit systems. The complement produced 0xFFFFFFFF7FFFFFFF instead of the intended 32-bit mask 0x7FFFFFFF. Applying this mask to the float32 value left the upper 32 bits set, corrupting the exponent when the value was later interpreted. This is classified as a [CWE-194] Sign Extension Error.
Root Cause
The root cause is the use of BIT(31) without explicit width control in a bitwise complement operation. BIT(31) returns type unsigned long, which on LP64 architectures is 64 bits wide. The complement operator inverts all 64 bits, producing a mask that fails to isolate the intended 32-bit float representation. Additionally, dense declaration and initialization syntax hindered code review and delayed detection.
Attack Vector
This defect is a data-integrity bug rather than a remotely exploitable memory-safety issue. Exploitation requires the presence of a Sensirion SCD30 sensor on the target system and read access to its iio sysfs interfaces. An attacker cannot trigger the bug remotely without existing local access, and the impact is limited to corrupted measurement output. No proof-of-concept exploit code is available for this issue. Consult the upstream kernel commits, including Kernel Git Commit 0ccff84 and Kernel Git Commit d49ff54, for the exact code changes.
Detection Methods for CVE-2026-64497
Indicators of Compromise
- Anomalous or wildly out-of-range CO2 concentration readings from SCD30-backed iio channels
- Kernel version strings that predate the fix commits on hosts using the scd30 driver
- Userspace telemetry pipelines showing inconsistent floating-point sensor values from /sys/bus/iio/devices/
Detection Strategies
- Inventory Linux hosts with the scd30 module loaded using lsmod | grep scd30 and cross-reference kernel build against the fixed commit hashes.
- Compare SCD30 sensor output against expected physical ranges to identify corrupted exponent artifacts.
- Track kernel package versions across the fleet and flag builds shipped before the upstream patch merges.
Monitoring Recommendations
- Alert on unexpected iio driver errors or invalid float reads in dmesg and journalctl output.
- Baseline SCD30 readings under known conditions and monitor for sudden order-of-magnitude changes.
- Include kernel driver commit hashes in configuration management inventory reports for affected industrial systems.
How to Mitigate CVE-2026-64497
Immediate Actions Required
- Apply the upstream stable kernel updates that include the iio: chemical: scd30 cleanup and sign-extension fix.
- Rebuild or update distribution kernels to a release that incorporates the referenced commits.
- Validate SCD30 sensor readings after patching to confirm correct exponent handling.
Patch Information
The fix is distributed across multiple stable kernel branches. Relevant commits include Kernel Git Commit 1821bca, Kernel Git Commit 40bb0fd, Kernel Git Commit 60d8779, Kernel Git Commit 82accdd, Kernel Git Commit 8d4a46e, and Kernel Git Commit b131f00. The patch includes linux/bitfield.h, adds FIELD_GET() based macros, and refactors variable initialization so mantissa, exp, and sign are handled separately.
Workarounds
- Unload the scd30 module (modprobe -r scd30_core scd30_i2c scd30_serial) on affected hosts where the sensor is not in active use.
- Perform sanity checks in userspace on all SCD30 float readings prior to acting on them until the patched kernel is deployed.
- Restrict local access to iio sysfs entries to trusted service accounts only.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
