CVE-2025-23142 sctp: detect and prevent references to a freed transport in sendmsg
A race condition in the Linux kernel SCTP implementation allows a use-after-free, potentially enabling local attackers to execute code or escalate privileges.
- 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-2025-23142?
CVE-2025-23142 is a high-severity use after free vulnerability in Debian Debian Linux, published on 1 May 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:
sctp: detect and prevent references to a freed transport in sendmsg
sctp_sendmsg() re-uses associations and transports when possible by doing a lookup based on the socket endpoint and the message destination address, and then sctp_sendmsg_to_asoc() sets the selected transport in all the message chunks to be sent.
There's a possible race condition if another thread triggers the removal of that selected transport, for instance, by explicitly unbinding an address with setsockopt(SCTP_SOCKOPT_BINDX_REM), after the chunks have been set up and before the message is sent. This can happen if the send buffer is full, during the period when the sender thread temporarily releases the socket lock in sctp_wait_for_sndbuf().
This causes the access to the transport data in sctp_outq_select_transport(), when the association outqueue is flushed, to result in a use-after-free read.
This change avoids this scenario by having sctp_transport_free() signal the freeing of the transport, tagging it as "dead". In order to do this, the patch restores the "dead" bit in struct sctp_transport, which was removed in commit 47faa1e4c50e ("sctp: remove the dead field of sctp_transport").
Then, in the scenario where the sender thread has released the socket lock in sctp_wait_for_sndbuf(), the bit is checked again after re-acquiring the socket lock to detect the deletion. This is done while holding a reference to the transport to prevent it from being freed in the process.
If the transport was deleted while the socket lock was relinquished, sctp_sendmsg_to_asoc() will return -EAGAIN to let userspace retry the send.
The bug was found by a private syzbot instance (see the error report [1] and the C reproducer that triggers it [2]).
Weakness: CWE-416
Which versions are affected by CVE-2025-23142?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-23142?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-23142 being exploited?
There is no known exploitation of CVE-2025-23142 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as BELL-CVE-2025-23142, DEBIAN-CVE-2025-23142, GHSA-q7q7-437c-qxh7, ROOT-OS-DEBIAN-12-CVE-2025-23142, ROOT-OS-UBUNTU-2204-CVE-2025-23142, ROOT-OS-UBUNTU-2404-CVE-2025-23142 and 1 more.