CVE-2026-98207 mmc: spi: reset bytes_xfered before retrying CRC failures
A flaw in the Linux kernel MMC SPI driver allows attackers to read stale data from previous failed transfers due to incorrect byte counting during CRC error retries.
- 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-2026-98207?
CVE-2026-98207 is a vulnerability in Linux, published on 6 Oct 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:
mmc: spi: reset bytes_xfered before retrying CRC failures
mmc_spi_data_do() updates data->bytes_xfered after each block has been transferred successfully. If a later block in the same data request fails with a CRC error, data->bytes_xfered may therefore contain the number of bytes completed before the failing block.
mmc_spi_request() has a private recovery path for such CRC failures. It sends STOP_TRANSMISSION, clears data->error and jumps back to crc_recover to issue the same command and data request again. However, it does not clear data->bytes_xfered before the retry.
If the retry succeeds, the request is completed with the bytes from the failed attempt still included in data->bytes_xfered. For a multi-block request this can make the completed request report more bytes than were transferred by the successful retry, and can even exceed the request size when most blocks completed before the CRC error.
This is most likely to be observed on MMC-over-SPI systems where long multi-block transfers occasionally hit a data CRC error but the mmc_spi-internal retry succeeds. The data itself is retried, but the completion accounting is not.
Clear data->bytes_xfered together with data->error before repeating the request so the final completion reports only the bytes transferred by the successful attempt.
Which versions are affected by CVE-2026-98207?
How do I fix CVE-2026-98207?
Apply the vendor's patch.
Is CVE-2026-98207 being exploited?
There is no known exploitation of CVE-2026-98207 in the wild and no public exploit code.
Sources
Also known as AZL-106002, BELL-CVE-2026-98207, DEBIAN-CVE-2026-98207, GHSA-gx8r-25rx-rh7g, UBUNTU-CVE-2026-98207.