CVE-2026-64327: usb: gadget: f_fs: Initialize epfile->in early to fix endpoint direction checks

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: 2026-07-25 · updated 2026-09-04

Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: Initialize epfile->in early to fix endpoint direction checks When parsing endpoint descriptors, ffs_data_got_descs() generates the eps_addrmap which contains the endpoint direction. However, epfile->in was previously only populated in ffs_func_eps_enable() which executes upon USB host connection. As a result, early userspace ioctls like FUNCTIONFS_DMABUF_ATTACH that run before the host connects would see epfile->in as 0, leading to incorrect DMA directions. By moving the initialization to ffs_epfiles_create(), epfile->in is accurate before userspace opens the endpoint files.

Affected products

Linux kernel: from 6.9 before 6.12.96; from 6.13 before 6.18.39; from 6.19 before 7.1.4; 7.2-rc1, 7.2-rc2 — fixed in 6.12.96, 6.18.39, 7.1.4

How to fix

Upgrade to a fixed version: Linux kernel 6.12.96, 6.18.39, 7.1.4. Check the vendor advisory for mitigations.

References

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