FreeBSD 12.0 RACK TCP Packet resource consumption

Summaryinfo

A vulnerability marked as problematic has been reported in FreeBSD 12.0. This impacts an unknown function of the component RACK Handler. The manipulation as part of TCP Packet leads to resource consumption. This vulnerability is referenced as CVE-2019-5599. Remote exploitation of the attack is possible. No exploit is available. Applying a patch is the recommended action to fix this issue.

Detailsinfo

A vulnerability was found in FreeBSD 12.0 (Operating System) and classified as problematic. This issue affects an unknown code of the component RACK Handler. The manipulation as part of a TCP Packet leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. Impacted is availability.

The weakness was published 06/19/2019 as FreeBSD-SA-19:08 as confirmed security advisory (Website). The advisory is shared at freebsd.org. The identification of this vulnerability is CVE-2019-5599 since 01/07/2019. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1499 for this issue. The advisory points out:

While processing acknowledgements, the RACK code uses several linked lists to maintain state entries. A malicious attacker can cause the lists to grow unbounded. This can cause an expensive list traversal on every packet being processed, leading to resource exhaustion and a denial of service.

Applying a patch is able to eliminate this problem. It is possible to mitigate the problem by applying the configuration setting kldunload tcp_rack. The best possible mitigation is suggested to be patching the affected component. A possible mitigation has been published immediately after the disclosure of the vulnerability. The security advisory contains the following remark:

By default RACK is not compiled or loaded into the TCP stack. To determine if you are using RACK, check the net.inet.tcp.functions_available sysctl. If it includes a line with "rack", the RACK stack is loaded.

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Productinfo

Type

• Operating System

Name

• FreeBSD

Version

• 12.0

License

• open-source

Website

• Product: https://www.freebsd.org/

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