CVE-2023-54085 mptcp: fix NULL pointer dereference on fastopen early fallback
A NULL pointer dereference in the Linux kernel MPTCP fastopen path allows attackers to cause a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-54085?
CVE-2023-54085 is a high-severity vulnerability in Linux, published on 24 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mptcp: fix NULL pointer dereference on fastopen early fallback
In case of early fallback to TCP, subflow_syn_recv_sock() deletes the subflow context before returning the newly allocated sock to the caller.
The fastopen path does not cope with the above unconditionally dereferencing the subflow context.
Which versions are affected by CVE-2023-54085?
How do I fix CVE-2023-54085?
Apply the vendor's patch.
Is CVE-2023-54085 being exploited?
There is no known exploitation of CVE-2023-54085 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2023-54085, GHSA-459f-v5p8-p6w3, UBUNTU-CVE-2023-54085.