SELinux Missing TCP Fast Open Permission Check in Linux Kernel

Executive Summary

This vulnerability in the Linux kernel involves SELinux not properly checking connect-related permissions when TCP Fast Open is used. TCP Fast Open allows faster connection establishment, but SELinux was not updated to enforce its security policies during this process. The fix ensures SELinux calls the correct permission check when the MSG_FASTOPEN flag is used in socket operations.

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Detection Guidance

This vulnerability affects SELinux's handling of TCP Fast Open connections. Detection requires checking kernel logs for SELinux denials related to TCP Fast Open or MSG_FASTOPEN flag usage. Use commands like dmesg | grep -i selinux or journalctl -k | grep -i selinux to review kernel logs for access denials.

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Impact Analysis

This vulnerability could allow unauthorized network connections to bypass SELinux security controls. An attacker might exploit it to establish connections without proper permission checks, potentially leading to unauthorized data access or network activity on systems using SELinux with TCP Fast Open.

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Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or other common standards and regulations. The issue is specific to SELinux permissions in the Linux kernel and does not involve data protection, privacy, or security controls that these regulations typically address.

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Mitigation Strategies

Apply the latest Linux kernel update that includes the SELinux fix for TCP Fast Open. If immediate patching is not possible, consider disabling TCP Fast Open temporarily via sysctl net.ipv4.tcp_fastopen=0 until the kernel is updated.

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