The Linux kernel USB serial driver keyspan_pda had a flaw in its write() callback implementation. After adding write FIFO support, the driver could return a count of characters submitted to the device that exceeded the number actually passed to write(). This caused the line discipline to continue writing data beyond the tty write buffer, resulting in an information leak. The fix ensures that keyspan_pda_write_start() returns zero on success, preventing the leak.

This vulnerability could lead to an information leak by allowing data beyond the intended write buffer to be read or transmitted. There is no indication of code execution or privilege escalation. No known exploits are reported in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The description states the issue has been resolved, implying a fix is available in updated Linux kernel versions. Users should apply official kernel updates once available.