CVE-2026-31452 ext4: convert inline data to extents when truncate exceeds inline size
A local attacker can trigger a kernel crash in the ext4 filesystem by truncating a file with inline data to a size exceeding inline capacity.
- 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-2026-31452?
CVE-2026-31452 is a high-severity denial of service vulnerability in Linux kernel, published on 22 Apr 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:
ext4: convert inline data to extents when truncate exceeds inline size
Add a check in ext4_setattr() to convert files from inline data storage to extent-based storage when truncate() grows the file size beyond the inline capacity. This prevents the filesystem from entering an inconsistent state where the inline data flag is set but the file size exceeds what can be stored inline.
Without this fix, the following sequence causes a kernel BUG_ON():
1. Mount filesystem with inode that has inline flag set and small size 2. truncate(file, 50MB) - grows size but inline flag remains set 3. sendfile() attempts to write data 4. ext4_write_inline_data() hits BUG_ON(write_size > inline_capacity)
The crash occurs because ext4_write_inline_data() expects inline storage to accommodate the write, but the actual inline capacity (~60 bytes for i_block + ~96 bytes for xattrs) is far smaller than the file size and write request.
The fix checks if the new size from setattr exceeds the inode's actual inline capacity (EXT4_I(inode)->i_inline_size) and converts the file to extent-based storage before proceeding with the size change.
This addresses the root cause by ensuring the inline data flag and file size remain consistent during truncate operations.
Weakness: CWE-787
Which versions are affected by CVE-2026-31452?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31452?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-31452 being exploited?
There is no known exploitation of CVE-2026-31452 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-83204, BELL-CVE-2026-31452, DEBIAN-CVE-2026-31452, GHSA-g495-4jqx-cp59, ROOT-OS-DEBIAN-11-CVE-2026-31452, ROOT-OS-DEBIAN-12-CVE-2026-31452 and 4 more.