# CVE-2026-63960: usb: typec: wcove: don't write past struct pd_message in wcove_read_rx_buffer()

> A malicious USB Type-C partner can trigger a buffer overflow in the Linux kernel WCOVE driver, potentially leading to code execution or privilege escalation.

- **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:** 20 Jul 2026
- **Also known as:** AZL-92778, BELL-CVE-2026-63960, DEBIAN-CVE-2026-63960, GHSA-5mqj-jpm9-chwp, ROOT-OS-UBUNTU-2204-CVE-2026-63960, UBUNTU-CVE-2026-63960

## What is CVE-2026-63960?

CVE-2026-63960 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: typec: wcove: don't write past struct pd_message in wcove_read_rx_buffer()

wcove_read_rx_buffer() copies the PD RX FIFO into the caller's
struct pd_message with

	for (i = 0; i < USBC_RXINFO_RXBYTES(info); i++)
		regmap_read(wcove->regmap, USBC_RX_DATA + i, msg + i);

which has two problems:

USBC_RXINFO_RXBYTES() is a 5-bit field (max 31) while struct pd_message
is 30 bytes (__le16 header + __le32 payload[PD_MAX_PAYLOAD], packed).
The byte count latched in RXINFO is the number of bytes the port partner
put on the wire, so a malicious partner that transmits a 31-byte frame
can drive the loop one byte past the destination if the WCOVE BMC
receiver does not enforce the PD object-count limit in hardware. The
existing FIXME flagged this as unverified.

Independently, regmap_read() takes an unsigned int * and stores a full
unsigned int at the destination. Passing the byte pointer msg + i means
each iteration writes four bytes; the high three are zero (val_bits is
8) and are normally overwritten by the next iteration, but the final
iteration's high bytes are not. With RXBYTES == 30 the i == 29 iteration
already writes three zero bytes past msg, which sits on the IRQ thread's
stack in wcove_typec_irq().

Clamp the loop to sizeof(struct pd_message) and read each register into
a local before storing only its low byte, so the copy can never exceed
the destination regardless of what RXINFO reports.

## Which versions are affected by CVE-2026-63960?


## How do I fix CVE-2026-63960?

Apply the vendor's patch.

## Is CVE-2026-63960 being exploited?

There is no known exploitation of CVE-2026-63960 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63960 and fix it if it is affected.

What it is: CVE-2026-63960 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-2026-63960 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-2026-63960/ (Markdown: https://insights.sbomify.com/CVE-2026-63960/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63960
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63960
- OSV: https://osv.dev/vulnerability/CVE-2026-63960

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63960/
Summaries are generated and may contain mistakes; the official description above is the record.