How CVE-2025-22003 Works
This vulnerability occurs in the Linux kernel’s CAN (Controller Area Network) subsystem, specifically in the `ucan` driver. The issue stems from an out-of-bound read during a `strscpy()` operation. The driver retrieves firmware version information via USB control messages but fails to ensure proper NULL termination. When `strscpy()` reads the source buffer (src
</code>), it checks one byte beyond the allocated buffer, leading to a memory access violation. This could allow an attacker to leak kernel memory or crash the system if malicious firmware data is provided.
The fix involves proper NULL termination of the firmware string immediately after retrieval via <code>usb_control_msg()</code>. Additionally, the payload structure is refactored to explicitly handle string termination, preventing unintended memory reads.
<h2 style="color: blue;">DailyCVE Form:</h2>
Platform: Linux Kernel
Version: Pre-5.15.120
Vulnerability: Out-of-Bound Read
Severity: Medium
Date: 04/10/2025
<h2 style="color: blue;">What Undercode Say:</h2>
<h2 style="color: blue;">Exploitation Analysis:</h2>
<ul>
<li>Triggered via malicious USB device emulating a UCAN adapter.</li>
<li>Exploitable if attacker controls firmware data passed to <code>usb_control_msg()</code>.</li>
<li>Kernel memory leak possible via partial read beyond buffer.</li>
</ul>
<h2 style="color: blue;">Protection Measures:</h2>
<h2 style="color: blue;">1. Patch to kernel version 5.15.120 or later.</h2>
<h2 style="color: blue;">2. Restrict USB device permissions via udev rules:</h2>
[bash]
SUBSYSTEM=="usb", ATTR{idVendor}=="XXXX", ATTR{idProduct}=="XXXX", MODE="0660", GROUP="plugdev"
3. Disable UCAN driver if unused:
echo "blacklist ucan" | sudo tee /etc/modprobe.d/ucan-blacklist.conf
Detection Commands:
- Check loaded UCAN module:
lsmod | grep ucan
- Verify kernel version:
uname -r
Proof-of-Concept (PoC) Snippet:
struct ucan_ctl_payload {
char fw_str[bash];
};
// Malicious payload with non-NULL terminated string
char exploit_fw[bash] = "malicious_firmware";
usb_control_msg(dev, USB_RECIP_DEVICE, UCAN_GET_FW, 0, 0, exploit_fw, UCAN_FW_STR_LEN, USB_CTRL_TIMEOUT);
Mitigation Code (Patch Example):
// Ensure NULL termination post usb_control_msg() ret = usb_control_msg(dev, USB_RECIP_DEVICE, UCAN_GET_FW, 0, 0, fw_str, UCAN_FW_STR_LEN - 1, USB_CTRL_TIMEOUT); fw_str[bash] = '\0';
References:
- Kernel Git commit: 7fdaf8966aae
- CVE Details: NVD CVE-2025-22003
References:
Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-22003
Extra Source Hub:
Undercode
