CVE-2022-48906 is a vulnerability identified in the Linux kernel's implementation of Multipath TCP (MPTCP), specifically related to the handling of the DATA_FIN timeout during retransmissions. The vulnerability arises from an integer shift operation that can go out-of-bounds when a large number of DATA_FIN retransmits occur. This was discovered using Syzkaller with Undefined Behavior Sanitizer (UBSAN), which detected a shift exponent of 32 applied to a 32-bit unsigned integer, an invalid operation causing undefined behavior. The root cause is in the net/mptcp/protocol.c source file, where the timeout calculation for DATA_FIN retransmissions does not properly limit the shift size, leading to potential integer overflow or logic errors. The Linux kernel patch corrects this by limiting the maximum timeout value through restricting the shift size, ensuring all intermediate calculations remain within valid bounds. Although no known exploits are currently reported in the wild, the vulnerability could theoretically be triggered by an attacker capable of inducing excessive retransmissions of DATA_FIN packets in an MPTCP session. This could lead to kernel instability or denial of service due to corrupted timeout values or unexpected kernel behavior. The vulnerability affects specific Linux kernel versions identified by commit hashes, including versions around 5.17.0-rc2, and is relevant to systems utilizing MPTCP, a protocol extension designed to improve TCP reliability and throughput by using multiple network paths simultaneously.

For European organizations, the impact of CVE-2022-48906 primarily concerns systems running Linux kernels with MPTCP enabled, particularly in environments where network reliability and multipath TCP are leveraged, such as data centers, cloud infrastructure, telecom providers, and enterprises with advanced networking setups. Exploitation could result in denial of service conditions on affected hosts, potentially disrupting critical services or applications dependent on stable network connectivity. This may affect confidentiality indirectly if service interruptions lead to fallback on less secure communication channels or cause operational disruptions. Integrity impact is limited but could arise if kernel instability leads to unpredictable system behavior. Availability is the most significant concern, as kernel crashes or hangs could cause outages. Given the lack of known exploits, the immediate risk is moderate; however, the vulnerability's presence in kernel code used widely across European servers and embedded devices means that unpatched systems remain at risk. Organizations with high availability requirements, such as financial institutions, healthcare providers, and critical infrastructure operators, should prioritize mitigation to avoid service disruptions.

To mitigate CVE-2022-48906, European organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from their distribution vendors or upstream Linux kernel sources. 2) Audit and monitor systems for the use of MPTCP; if MPTCP is not required, consider disabling it to reduce the attack surface. 3) Implement network-level controls to detect and limit abnormal retransmission patterns that could trigger the vulnerability. 4) Employ kernel hardening and runtime protection mechanisms such as kernel address space layout randomization (KASLR), seccomp filters, and kernel lockdown features to reduce the impact of potential exploitation. 5) Maintain robust incident response and monitoring to detect signs of kernel instability or denial of service events related to network traffic anomalies. 6) Coordinate with Linux distribution maintainers and security teams to ensure timely updates and vulnerability awareness. 7) For critical systems, consider deploying kernel live patching solutions to minimize downtime during patch application.