An issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers (ISNs) for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing ones or spoof future ones. While the ISN generator seems to adhere to RFC 793 (where a global 32-bit counter is incremented roughly every 4 microseconds), proper ISN generation should aim to follow at least the specifications outlined in RFC 6528.

An issue was discovered in Ethernut Nut/OS 5.1. The code that generates Initial Sequence Numbers (ISNs) for TCP connections derives the ISN from an insufficiently random source. As a result, an attacker may be able to determine the ISN of current and future TCP connections and either hijack existing ones or spoof future ones. While the ISN generator seems to adhere to RFC 793 (where a global 32-bit counter is incremented roughly every 4 microseconds), proper ISN generation should aim to follow at least the specifications outlined in RFC 6528.

Nut/Net software relies on highly predictable source values and has consistent increments when generating initial sequence numbers (ISN), which may allow an attacker to spoof or disrupt TCP connections.CVE-2020-27213 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N). uC/TCP-IP ISN generation relies on a linear congruential generator (LCG), which is reversable from observed output streams as the algorithm is seeded with publicly recoverable information. This defect may allow an attacker to spoof or disrupt TCP connections.CVE-2020-27630 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N). CycloneTCP ISN generation relies on a linear congruential generator (LCG), which is reversable from observed output streams as the algorithm is seeded with publicly recoverable information. This defect may allow an attacker to spoof or disrupt TCP connections.CVE-2020-27631 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N). NDKTCPIP software is initialized with a consistent value and has consistent increments when generating initial sequence numbers (ISN), which may allow an attacker to spoof or disrupt TCP connections.CVE-2020-27632 has been assigned to this vulnerability. A CVSS v3 bas…

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in TCP/IP Stack ausnutzen, um beliebigen Programmcode auszuführen, einen Denial-of-Service-Zustand herbeiführen oder Sicherheitsvorkehrungen umgehen.