CVE-2026-99137 cifs: don't update i_size in cifs_do_truncate without a cached handle
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99137?
CVE-2026-99137 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
cifs: don't update i_size in cifs_do_truncate without a cached handle
If find_writable_file() returns null, cifs_file_flush will return 0 without issuing set_file_size, and the outer 'if (!rc)' block will set i_size to 0 before telling the server to truncate. If the cifs_open() then fails, the inode will have size 0, while the server file is unchanged.
Move the netfs_resize_file() and cifs_setsize() into the 'if (cfile)', so they only run after a successful set_file_size.
In the no-handle else branch, evict stale pages with truncate_inode_pages before the O_TRUNC open to dispose of old cache pages, and let the open response set the i_size.
Which versions are affected by CVE-2026-99137?
How do I fix CVE-2026-99137?
Upgrade to a fixed version.
Is CVE-2026-99137 being exploited?
There is no known exploitation of CVE-2026-99137 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-99137, DEBIAN-CVE-2026-99137, GHSA-4m2c-p8vw-33gr, UBUNTU-CVE-2026-99137.