CVE-2024-53176: Linux kernel · smb: During unmount, ensure all cached dir instances drop their dentry
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical · fixed in 6.8.0-1027.29~22.04.1 : patch Linux kernel as a priority.
Data as of 28 Oct 2026, 11:13 UTC
- Patch
- Available – fixed in 6.8.0-1027.29~22.04.1, 6.8.0-1027.32~22.04.1, 6.8.0-1028.30~22.04.1 +29
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Dec 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7276-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7277-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7310-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7449-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7450-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7451-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7452-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7453-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7449-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7468-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7523-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7524-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-nvidiapkg:deb/ubuntu/linux-azure-nvidia?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: smb: During unmount, ensure all cached dir instances drop their dentry The unmount process (cifs_kill_sb() calling close_all_cached_dirs()) can race with various cached directory operations, which ultimately results in dentries not being dropped and these kernel BUGs: BUG: Dentry ffff88814f37e358{i=1000000000080,n=/} still in use (2) [unmount of cifs cifs] VFS: Busy inodes after unmount of cifs (cifs) ------------[ cut here ]------------ kernel BUG at fs/super.c:661! This happens when a cfid is in the process of being cleaned up when, and has been removed from the cfids->entries list, including: - Receiving a lease break from the server - Server reconnection triggers invalidate_all_cached_dirs(), which removes all the cfids from the list - The laundromat thread decides to expire an old cfid. To solve these problems, dropping the dentry is done in queued work done in a newly-added cfid_put_wq workqueue, and close_all_cached_dirs() flushes that workqueue after it drops all the dentries of which it's aware. This is a global workqueue (rather than scoped to a mount), but the queued work is minimal. The final cleanup work for cleaning up a cfid is performed via work queued in the serverclose_wq workqueue; this is done separate from dropping the dentries so that close_all_cached_dirs() doesn't block on any server operations. Both of these queued works expect to invoked with a cfid reference and a tcon reference to avoid those objects from being freed while the work is ongoing. While we're here, add proper locking to close_all_cached_dirs(), and locking around the freeing of cfid->dentry.
References
- ubuntu.com/security/CVE-2024-53176 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2024-53176 (opens in a new tab)
- git.kernel.org/linus/3fa640d035e5ae526769615c35cb9ed4be6e3662 (opens in a new tab)
- git.kernel.org/stable/c/3fa640d035e5ae526769615c35cb9ed4be6e3662 (opens in a new tab)
- git.kernel.org/stable/c/548812afd96982a76a93ba76c0582ea670c40d9e (opens in a new tab)
- git.kernel.org/stable/c/73934e535cffbda1490fa97d82690a0f9aa73e94 (opens in a new tab)
- git.kernel.org/stable/c/ff4528bbc82d0d90073751f7b49e7b9e9c7e5638 (opens in a new tab)
- ubuntu.com/security/notices/USN-7276-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7277-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7310-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7449-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7450-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7451-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7452-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7453-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7449-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7468-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7523-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7524-1 (opens in a new tab)