Description

In the Linux kernel, the following vulnerability has been resolved:

can: ucan: fix out of bound read in strscpy() source

Commit 7fdaf8966aae ("can: ucan: use strscpy() to instead of strncpy()")
unintentionally introduced a one byte out of bound read on strscpy()'s
source argument (which is kind of ironic knowing that strscpy() is meant
to be a more secure alternative :)).

Let's consider below buffers:

dest[len + 1]; /* will be NUL terminated */
src[len]; /* may not be NUL terminated */

When doing:

strncpy(dest, src, len);
dest[len] = '\0';

strncpy() will read up to len bytes from src.

On the other hand:

strscpy(dest, src, len + 1);

will read up to len + 1 bytes from src, that is to say, an out of bound
read of one byte will occur on src if it is not NUL terminated. Note
that the src[len] byte is never copied, but strscpy() still needs to
read it to check whether a truncation occurred or not.

This exact pattern happened in ucan.

The root cause is that the source is not NUL terminated. Instead of
doing a copy in a local buffer, directly NUL terminate it as soon as
usb_control_msg() returns. With this, the local firmware_str[] variable
can be removed.

On top of this do a couple refactors:

- ucan_ctl_payload->raw is only used for the firmware string, so
rename it to ucan_ctl_payload->fw_str and change its type from u8 to
char.

- ucan_device_request_in() is only used to retrieve the firmware
string, so rename it to ucan_get_fw_str() and ...

Classification

CVE ID: CVE-2025-22003

Affected Products

Vendor: Linux, Linux

Product: Linux, Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.01% (probability of being exploited)

EPSS Percentile: 1.35% (scored less or equal to compared to others)

EPSS Date: 2025-04-18 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-22003
https://git.kernel.org/stable/c/cc29775a8a72d7f3b56cc026796ad99bd65804a7
https://git.kernel.org/stable/c/8cec9e314d3360fc1d8346297c41a6ee45cb45a9
https://git.kernel.org/stable/c/a4994161a61bc8fd71d105c579d847cefee99262
https://git.kernel.org/stable/c/1d22a122ffb116c3cf78053e812b8b21f8852ee9

Timeline