CVE-2026-89642 cifs: call pagecache_isize_extended() in cifs_setsize() when extending
A local attacker can read stale memory data from the page cache when extending a CIFS file size, potentially exposing sensitive information.
- 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-2026-89642?
CVE-2026-89642 is a vulnerability in Linux, published on 11 Sep 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:
cifs: call pagecache_isize_extended() in cifs_setsize() when extending
cifs_setsize() calls truncate_pagecache() but skips pagecache_isize_extended() on extension. truncate_setsize() shows the correct pattern:
i_size_write(inode, newsize); if (newsize > oldsize) pagecache_isize_extended(inode, oldsize, newsize); truncate_pagecache(inode, newsize);
pagecache_isize_extended() zeroes the tail of the page straddling old EOF. Without it, dirty bytes in that region can be written back to the server, exposing stale data in the newly extended range.
Which versions are affected by CVE-2026-89642?
How do I fix CVE-2026-89642?
Apply the vendor's patch.
Is CVE-2026-89642 being exploited?
There is no known exploitation of CVE-2026-89642 in the wild and no public exploit code.
Sources
Also known as AZL-100884, BELL-CVE-2026-89642, DEBIAN-CVE-2026-89642, GHSA-cjwf-376p-qpm9, UBUNTU-CVE-2026-89642.