CVE-2023-54099 fs: Protect reconfiguration of sb read-write from racing writes
A race condition in Linux kernel filesystem remounting allows local attackers to bypass read-only protections, potentially leading to privilege escalation or data corruption.
- 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-2023-54099?
CVE-2023-54099 is a vulnerability in Linux, published on 24 Dec 2025. 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:
fs: Protect reconfiguration of sb read-write from racing writes
The reconfigure / remount code takes a lot of effort to protect filesystem's reconfiguration code from racing writes on remounting read-only. However during remounting read-only filesystem to read-write mode userspace writes can start immediately once we clear SB_RDONLY flag. This is inconvenient for example for ext4 because we need to do some writes to the filesystem (such as preparation of quota files) before we can take userspace writes so we are clearing SB_RDONLY flag before we are fully ready to accept userpace writes and syzbot has found a way to exploit this [1]. Also as far as I'm reading the code the filesystem remount code was protected from racing writes in the legacy mount path by the mount's MNT_READONLY flag so this is relatively new problem. It is actually fairly easy to protect remount read-write from racing writes using sb->s_readonly_remount flag so let's just do that instead of having to workaround these races in the filesystem code.
[1] https://lore.kernel.org/all/[email protected]/T/
Which versions are affected by CVE-2023-54099?
How do I fix CVE-2023-54099?
Apply the vendor's patch.
Is CVE-2023-54099 being exploited?
There is no known exploitation of CVE-2023-54099 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2023-54099, DEBIAN-CVE-2023-54099, GHSA-vwq3-xpg9-vpx4, UBUNTU-CVE-2023-54099.