CVE-2025-23142 is a use-after-free vulnerability in the Linux kernel's SCTP (Stream Control Transmission Protocol) implementation, specifically within the sctp_sendmsg() function. SCTP is a transport-layer protocol used for message-oriented communication, often in telecommunications and other specialized network applications. The vulnerability arises due to a race condition where the transport associated with an SCTP message can be freed by another thread while the sending thread temporarily releases the socket lock during send buffer wait (in sctp_wait_for_sndbuf()). This occurs when the sender thread sets up message chunks referencing a transport, but before the message is sent, another thread removes the transport (e.g., by unbinding an address via setsockopt with SCTP_SOCKOPT_BINDX_REM). The race leads to a use-after-free read in sctp_outq_select_transport() when the association outqueue is flushed, potentially causing kernel memory corruption or crashes. The patch to fix this issue reintroduces a "dead" bit in the sctp_transport structure to mark transports as freed and signals this state. After reacquiring the socket lock, the sender thread checks this bit and, if the transport was freed, returns -EAGAIN to userspace to retry sending, preventing use-after-free access. The bug was discovered by a private syzbot instance and is confirmed with a C reproducer. No known exploits are reported in the wild yet, and no CVSS score has been assigned. The vulnerability affects multiple Linux kernel versions identified by commit hashes, indicating a broad impact across kernel releases that include the vulnerable SCTP code.

For European organizations, this vulnerability poses a risk primarily to systems running Linux kernels with SCTP enabled and in use. SCTP is commonly used in telecommunications infrastructure, signaling systems, and certain industrial or specialized network environments. Exploitation could lead to kernel crashes (denial of service) or potentially memory corruption, which might be leveraged for privilege escalation or arbitrary code execution, though no public exploits are known yet. Organizations operating telecom networks, critical infrastructure, or industrial control systems in Europe that rely on Linux-based systems with SCTP are at higher risk. Disruption of these systems could impact service availability, data integrity, and operational continuity. Given the kernel-level nature of the vulnerability, successful exploitation could compromise the confidentiality and integrity of affected systems. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time. The vulnerability's race condition complexity may limit exploitability but does not preclude targeted attacks against high-value infrastructure.

European organizations should prioritize updating their Linux kernels to versions that include the patch for CVE-2025-23142 as soon as vendor updates become available. Since the vulnerability involves a race condition in SCTP transport handling, disabling SCTP support on systems where it is not required can reduce the attack surface. For systems that must use SCTP, implementing strict access controls and monitoring for unusual kernel behavior or crashes can help detect exploitation attempts. Network segmentation to isolate critical SCTP-using infrastructure and limiting administrative access to systems running vulnerable kernels are recommended. Additionally, organizations should review and harden socket option usage related to SCTP (e.g., setsockopt calls) to prevent unauthorized address unbinding. Employing kernel live patching solutions where available can reduce downtime during patch deployment. Finally, maintaining up-to-date intrusion detection systems with SCTP protocol anomaly detection can provide early warnings of exploitation attempts.