TLDR: Misconfigured nftables, introduced in 2014 as the successor to iptables, can result in security vulnerabilities, unexpected traffic filtering, and operational disruptions. Issues such as improperly defined rules, incorrect priorities in chains, or missing default policies can lead to unauthorized access, blocked legitimate traffic, or ineffective network segmentation.

https://en.wikipedia.org/wiki/Nftables

One of the common challenges with misconfigured nftables is the use of overly permissive or conflicting rules in rule sets. For example, forgetting to establish a default-deny policy can allow unintended traffic through the firewall. Additionally, errors in rule syntax or sequence, such as defining rules that contradict each other, can result in unpredictable behavior, including blocking or allowing critical traffic incorrectly. Lack of proper logging configurations further complicates troubleshooting these issues.

https://wiki.nftables.org/wiki-nftables/index.php/Main_Page

To avoid misconfigurations, administrators should adopt best practices such as using a structured approach to rule creation, enabling verbose logging for monitoring, and testing configurations in a controlled environment before deployment. Tools like nft's built-in testing features and third-party auditing scripts can help identify and fix configuration gaps. Consistent updates to nftables ensure compatibility with newer kernel features and enhance its security and functionality for dynamic and complex network setups.

https://wiki.nftables.org/wiki-nftables/index.php/Configuring_nftables