CVE-2022-26966

What it actually does

The sr9700 USB network driver in the Linux kernel before 5.16.12 performs insufficient validation of frame lengths received from a connected device, allowing an attacker to trigger an out-of-bounds read that leaks uninitialized heap memory contents to user space.

Why it matters to the business

Attackers with physical or local access can obtain sensitive kernel data such as credentials or encryption keys from affected Linux systems, raising the risk of credential theft and subsequent lateral movement or data breaches.

How an attack unfolds

An attacker attaches a malicious USB device that registers as an sr9700 adapter; the driver is loaded and the device sends crafted Ethernet frames containing manipulated length values, causing the kernel to copy more data than intended from the heap into a response buffer that is then readable by the attacker.

How to fix it

Upgrade the Linux kernel to 5.16.12 or newer; apply commit e9da0b56fe27206b49f39805f7dcda8a89379062 which adds proper length validation in drivers/net/usb/sr9700.c. Where immediate patching is not possible, restrict untrusted USB devices via USBGuard or kernel module blacklisting.

How to confirm the fix worked

Confirm the running kernel version is 5.16.12 or later; inspect the sr9700.c source for the length-check logic introduced by commit e9da0b56fe27206b49f39805f7dcda8a89379062; test with a fuzzer that sends variable-length frames and verify no excess data is returned.

Typical attack path

1. Physically connect or emulate a malicious USB device recognized by the sr9700 driver
2. Trigger driver initialization and frame reception path
3. Transmit multiple frames with crafted length fields
4. Read the resulting heap memory disclosure from the returned buffers
5. Parse leaked data for credentials or other sensitive kernel artifacts

How to detect it

Review kernel logs for sr9700 driver entries around USB attach events; correlate with unexpected process access to network device files; no reliable post-exploitation artifacts are known because the flaw only discloses memory without leaving persistent traces.

What your security team should do

• Prioritize kernel upgrade to the fixed version on all exposed systems
• Implement USB device allow-listing to limit exposure to untrusted hardware
• Monitor kernel logs for sr9700 driver anomalies during the patching window
• Review systems for any prior local USB device attachments that could have triggered the flaw