# CVE-2026-68478: memstick: ms_block: reject a card that reports too many blocks

> A malicious Memory Stick card can trigger a buffer overflow in the Linux kernel memstick driver, potentially allowing local attackers to execute code or escalate privileges.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-68478, DEBIAN-CVE-2026-68478, GHSA-ppgx-492f-63h6, UBUNTU-CVE-2026-68478

## What is CVE-2026-68478?

CVE-2026-68478 is a memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

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

memstick: ms_block: reject a card that reports too many blocks

msb_ftl_initialize() computes the zone count from the card block count
with no bound:

	msb->zone_count = msb->block_count / MS_BLOCKS_IN_ZONE;
	...
	for (i = 0; i < msb->zone_count; i++)
		msb->free_block_count[i] = MS_BLOCKS_IN_ZONE;

msb->block_count is a card value. msb_read_boot_blocks() reads
number_of_blocks from the card boot page and byte swaps it.
free_block_count is a fixed int[MS_MAX_ZONES]. MS_MAX_ZONES is 16, so the
valid indices are 0 to 15. The init loop above indexes it by zone_count.
msb_mark_block_used() and msb_mark_block_unused() index it by
pba / MS_BLOCKS_IN_ZONE, for pba up to block_count - 1. A card may report
up to 65535 blocks. A block_count above 8192 (MS_MAX_ZONES *
MS_BLOCKS_IN_ZONE) lets the pba index reach 16. That writes past
free_block_count[] and corrupts struct msb_data. A larger count runs the
init loop past the end too.

A real Memory Stick has at most 16 zones. So it has at most 8192 blocks.
msb_ftl_initialize() now rejects a card that reports more than
MS_MAX_ZONES * MS_BLOCKS_IN_ZONE blocks.

## Which versions are affected by CVE-2026-68478?


## How do I fix CVE-2026-68478?

Apply the vendor's patch.

## Is CVE-2026-68478 being exploited?

There is no known exploitation of CVE-2026-68478 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68478 and fix it if it is affected.

What it is: CVE-2026-68478 is a memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-68478 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-2026-68478/ (Markdown: https://insights.sbomify.com/CVE-2026-68478/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68478
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68478
- OSV: https://osv.dev/vulnerability/CVE-2026-68478

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68478/
Summaries are generated and may contain mistakes; the official description above is the record.