CVE-2026-72142 i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)
A flaw in the Linux kernel i2c imx driver causes a bus lockup during specific SMBus block reads, requiring a power cycle to recover.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72142?
CVE-2026-72142 is a denial of service 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:
i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)
SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the atomic (polling) path rejects it as -EPROTO. Worse, it returns without a NACK+STOP: the next receive cycle has already started, so the target keeps holding SDA and the bus stays stuck until a power cycle for this i2c controller.
Reading I2DR to obtain the count likewise arms the next byte on the count > I2C_SMBUS_BLOCK_MAX path, which also returned -EPROTO directly and left the bus held.
Handle both: NACK the in-flight dummy byte (TXAK) and extend msgs->len so the existing last-byte handling emits STOP; the dummy byte is discarded. A count of 0 is a valid empty block read; a count above I2C_SMBUS_BLOCK_MAX is still reported as -EPROTO, but only after the bus has been released.
The interrupt-driven path has the same flaw from a later commit and is fixed separately, as it carries a different Fixes: tag and stable range.
Which versions are affected by CVE-2026-72142?
How do I fix CVE-2026-72142?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-72142 being exploited?
There is no known exploitation of CVE-2026-72142 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72142, DEBIAN-CVE-2026-72142, GHSA-63x6-874m-qjjg, UBUNTU-CVE-2026-72142.