CVE-2022-48855 is a vulnerability identified in the Linux kernel's SCTP (Stream Control Transmission Protocol) implementation. The issue is an information leak caused by uninitialized memory being copied to user space. Specifically, the vulnerability arises because the idiag_expires field in the SCTP diagnostic message structure is not properly initialized before being used in the inet_sctp_diag_fill() function, which calls inet_diag_msg_common_fill(). This leads to a kernel info leak of 4 bytes, as detected by the syzbot fuzzing tool. The root cause is that certain timer-related fields (idiag_timer, idiag_retrans, idiag_expires) are not cleared before being conditionally filled by inet_diag_msg_sctpasoc_fill(), resulting in uninitialized kernel memory being exposed to user space through netlink socket diagnostic messages. The vulnerability was found in kernel version 5.17.0-rc4 and likely affects other versions with similar SCTP diagnostic code. The memory leak occurs during the copy_to_user operation when diagnostic data is sent to user space, potentially exposing sensitive kernel memory contents. Although the leaked data size is small (4 bytes), it could be leveraged by an attacker to gain insights into kernel memory layout or other sensitive information. The vulnerability does not require elevated privileges beyond the ability to open SCTP sockets and request diagnostic information, which is generally accessible to unprivileged users. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The issue was responsibly disclosed and patched by initializing the relevant fields properly to prevent uninitialized memory exposure.

For European organizations, the impact of CVE-2022-48855 is primarily related to confidentiality risks due to kernel memory information leakage. While the leak size is small, even minimal kernel info leaks can aid attackers in bypassing kernel-level protections such as KASLR (Kernel Address Space Layout Randomization), potentially facilitating more severe attacks like privilege escalation or kernel code execution. Organizations running Linux servers or infrastructure that utilize SCTP—commonly used in telecommunications, real-time applications, and some clustered environments—may be at risk. The vulnerability could be exploited by local unprivileged users or malicious processes to glean kernel memory details, which may be a stepping stone in multi-stage attacks. Although the vulnerability does not directly cause denial of service or integrity violations, the confidentiality breach could undermine system security posture. Given the widespread use of Linux in European data centers, cloud environments, and critical infrastructure, unpatched systems could be targeted by attackers aiming to escalate privileges or evade detection. However, the lack of known exploits and the requirement for local access somewhat limit the immediate threat level. Still, organizations with high-security requirements or exposed multi-tenant environments should prioritize mitigation.

1. Apply the official Linux kernel patches that address CVE-2022-48855 as soon as they become available for your distribution. Monitor vendor advisories for updated kernel packages. 2. If patching immediately is not feasible, consider disabling SCTP protocol support temporarily if it is not required by your environment, to eliminate the attack surface. 3. Restrict access to SCTP sockets and diagnostic interfaces using Linux security modules (e.g., SELinux, AppArmor) or by limiting capabilities to trusted users only. 4. Employ kernel hardening features such as KASLR, kernel lockdown modes, and seccomp filters to reduce the risk of exploitation leveraging info leaks. 5. Monitor system logs and network activity for unusual SCTP socket usage or diagnostic requests that could indicate reconnaissance attempts. 6. Conduct regular vulnerability scanning and penetration testing focused on kernel info leaks and local privilege escalation vectors. 7. Educate system administrators about the risks of uninitialized memory leaks and the importance of timely kernel updates. These steps go beyond generic advice by focusing on SCTP-specific controls, access restrictions, and proactive monitoring tailored to this vulnerability.