CVE-2025-21704

Summary

In the Linux kernel, the following vulnerability has been resolved: usb: cdc-acm: Check control transfer buffer size before access If the first fragment is shorter than struct usb_cdc_notification, we can't calculate an expected_size. Log an error and discard the notification instead of reading lengths from memory outside the received data, which can lead to memory corruption when the expected_size decreases between fragments, causing `expected_size - acm->nb_index` to wrap. This issue has been present since the beginning of git history; however, it only leads to memory corruption since commit ea2583529cd1 ("cdc-acm: reassemble fragmented notifications"). A mitigating factor is that acm_ctrl_irq() can only execute after userspace has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will do that automatically depending on the USB device's vendor/product IDs and its other interfaces.

Impact & exploitability

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products we track (1)

Recommendation

Apply the vendor fix promptly. Open any affected product above for its exact safe version.

Official patch: https://git.kernel.org/stable/c/383d516a0ebc8641372b521c8cb717f0f1834831 ↗

Additional information

• NVD record
• https://git.kernel.org/stable/c/383d516a0ebc8641372b521c8cb717f0f1834831Patch
• https://git.kernel.org/stable/c/6abb510251e75f875797d8983a830e6731fa281cPatch
• https://git.kernel.org/stable/c/7828e9363ac4d23b02419bf2a45b9f1d9fb35646Patch
• https://git.kernel.org/stable/c/871619c2b78fdfe05afb4e8ba548678687beb812Patch
• https://git.kernel.org/stable/c/90dd2f1b7342b9a671a5ea4160f408037b92b118Patch
• https://git.kernel.org/stable/c/a4e1ae5c0533964170197e4fb4f33bc8c1db5cd2Patch
• https://git.kernel.org/stable/c/e563b01208f4d1f609bcab13333b6c0e24ce6a01Patch
• https://git.kernel.org/stable/c/f64079bef6a8a7823358c3f352ea29a617844636Patch