# CVE-2026-63903: USB: serial: belkin_sa: validate interrupt status length

> A missing length check in the Belkin USB serial driver allows out-of-bounds reads, potentially causing kernel crashes or information disclosure via local physical access.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Jul 2026
- **Updated:** 19 Jul 2026
- **Also known as:** BELL-CVE-2026-63903, DEBIAN-CVE-2026-63903, GHSA-5c4f-qfw8-c34w, ROOT-OS-UBUNTU-2204-CVE-2026-63903, UBUNTU-CVE-2026-63903

## What is CVE-2026-63903?

CVE-2026-63903 is a memory corruption vulnerability in Linux, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

USB: serial: belkin_sa: validate interrupt status length

The Belkin interrupt callback treats interrupt data as a four-byte
status report and reads LSR/MSR fields at offsets 2 and 3. The
interrupt-in buffer length is derived from endpoint wMaxPacketSize, and
short interrupt transfers may complete successfully with a smaller
actual_length.

Check the completed interrupt packet length before parsing status
fields so short interrupt endpoints and short successful packets are
ignored instead of causing out-of-bounds or stale status-byte reads.

KASAN report as below:

BUG: KASAN: slab-out-of-bounds in belkin_sa_read_int_callback()
Read of size 1
Call trace:
  belkin_sa_read_int_callback() (drivers/usb/serial/belkin_sa.c:202)
  __usb_hcd_giveback_urb() (drivers/usb/core/hcd.c:1630)
  dummy_timer() (?:?)

## Which versions are affected by CVE-2026-63903?


## How do I fix CVE-2026-63903?

Apply the vendor's patch.

## Is CVE-2026-63903 being exploited?

There is no known exploitation of CVE-2026-63903 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63903 and fix it if it is affected.

What it is: CVE-2026-63903 is a memory corruption vulnerability in Linux, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-63903 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-63903/ (Markdown: https://insights.sbomify.com/CVE-2026-63903/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63903
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63903
- OSV: https://osv.dev/vulnerability/CVE-2026-63903

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63903/
Summaries are generated and may contain mistakes; the official description above is the record.