CVE-2026-31412: usb: gadget: f_mass_storage: Fix potential integer overflow in check_command_size_in_blocks()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-10 · updated 2026-06-17
Weakness: CWE-190

Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_mass_storage: Fix potential integer overflow in check_command_size_in_blocks() The `check_command_size_in_blocks()` function calculates the data size in bytes by left shifting `common->data_size_from_cmnd` by the block size (`common->curlun->blkbits`). However, it does not validate whether this shift operation will cause an integer overflow. Initially, the block size is set up in `fsg_lun_open()` , and the `common->data_size_from_cmnd` is set up in `do_scsi_command()`. During initialization, there is no integer overflow check for the interaction between two variables. So if a malicious USB host sends a SCSI READ or WRITE command requesting a large amount of data (`common->data_size_from_cmnd`), the left shift operation can wrap around. This results in a truncated data size, which can bypass boundary checks and potentially lead to memory corruption or out-of-bounds accesses. Fix this by using the check_shl_overflow() macro to safely perform the shift and catch any overflows.

Affected products

Linux kernel: from 3.3 before 6.1.167; from 6.2 before 6.6.130; from 6.7 before 6.12.78; from 6.13 before 6.18.19; from 6.19 before 6.19.9; 7.0-rc1, 7.0-rc2, 7.0-rc3, 7.0-rc4 — fixed in 6.1.167, 6.12.78, 6.18.19, 6.19.9, 6.6.130

How to fix

Upgrade to a fixed version: Linux kernel 6.1.167, 6.12.78, 6.18.19, 6.19.9. Check the vendor advisory for mitigations.

References

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