CVE-2026-74308 ext4: fix kernel BUG in ext4_write_inline_data_end
A local attacker can trigger a kernel crash in the ext4 filesystem when using the data=journal mount option, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74308?
CVE-2026-74308 is a denial of service vulnerability in Linux, published on 15 Aug 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: fix kernel BUG in ext4_write_inline_data_end
When the data=journal mount option is used, the ext4_journalled_write_end() function incorrectly calls ext4_write_inline_data_end() without checking if the EXT4_STATE_MAY_INLINE_DATA flag is still set on the inode.
If a previous attempt to convert the inline data to an extent failed (e.g. due to ENOSPC), the EXT4_STATE_MAY_INLINE_DATA flag is cleared, but the EXT4_INODE_INLINE_DATA flag remains set. In this scenario, the next call to ext4_write_begin() will not prepare the inline data xattr for writing, but ext4_journalled_write_end() will incorrectly attempt to write to it, triggering a BUG_ON(pos + len > EXT4_I(inode)->i_inline_size) in ext4_write_inline_data() since i_inline_size was not expanded.
Fix this by ensuring that ext4_journalled_write_end() only calls ext4_write_inline_data_end() if the EXT4_STATE_MAY_INLINE_DATA flag is set, mirroring the behavior of ext4_write_end() and ext4_da_write_end().
Which versions are affected by CVE-2026-74308?
How do I fix CVE-2026-74308?
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-2026-74308 being exploited?
There is no known exploitation of CVE-2026-74308 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74308, DEBIAN-CVE-2026-74308, GHSA-grvr-g5pp-pc9x, UBUNTU-CVE-2026-74308.