CVE-2026-98685 smb: client: discard post-EOF pagecache when extending a file via clone range
A local attacker can read stale pagecache data past the end of file when extending files via SMB clone operations in the Linux kernel.
- 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-2026-98685?
CVE-2026-98685 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: discard post-EOF pagecache when extending a file via clone range
cifs_remap_file_range() discarded the pagecache only for the folios overlapping the destination region, so when a clone extends the file the folio straddling the old EOF - which may hold data dirtied past EOF through an mmap - was never dropped and became visible as file content once the file was extended.
Start the discard at the smaller of fstart and the old EOF. i_size is still old here, so nothing past the old EOF is flushed to the server.
Which versions are affected by CVE-2026-98685?
How do I fix CVE-2026-98685?
Apply the vendor's patch.
Is CVE-2026-98685 being exploited?
There is no known exploitation of CVE-2026-98685 in the wild and no public exploit code.
Sources
Also known as AZL-108978, BELL-CVE-2026-98685, DEBIAN-CVE-2026-98685, GHSA-r85p-j355-crhr, UBUNTU-CVE-2026-98685.