CVE-2026-98683 smb: client: flush dirty data before zeroing a range
A race condition in the Linux kernel SMB client allows attackers to read stale data from zeroed file ranges due to missing dirty page flushes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98683?
CVE-2026-98683 is a vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
smb: client: flush dirty data before zeroing a range
smb3_zero_range() emulates FALLOC_FL_ZERO_RANGE by invalidating the page cache over the target range with truncate_pagecache_range() and then issuing FSCTL_SET_ZERO_DATA to the server.
Dirty data was only flushed conditionally, when the range reached or extended EOF. For a purely interior zero range that does not reach EOF, no flush happened, so a dirty folio overlapping the range could be written back to the server after the FSCTL and refill the range that was just zeroed with stale data.
Fix this by unconditionally flushing and waiting for dirty data in the range before invalidating the page cache and issuing FSCTL_SET_ZERO_DATA, exactly as was done for smb3_punch_hole() in commit d7d2adcd022b ("smb/client: flush dirty data before punching a hole"); the two paths are structurally identical here.
This is observed as generic/363 randomly reading stale data where a zeroed range is expected against Windows Server.
Which versions are affected by CVE-2026-98683?
How do I fix CVE-2026-98683?
Apply the vendor's patch.
Is CVE-2026-98683 being exploited?
There is no known exploitation of CVE-2026-98683 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-98683, DEBIAN-CVE-2026-98683, GHSA-f8wg-49h3-2qvh, UBUNTU-CVE-2026-98683.