Log4j vulnerability – what everyone needs to know post, december 14, 2021april 26, 2024 Log4shell is a critical vulnerability in the widely-used logging tool Log4j, which is used by millions of computers worldwide running online services. A wide range of people, including organisations, governments and individuals are likely to be affected by it. Although fixes have been issued, they will still need to be implemented. What the Log4j vulnerability is, who is affected – NCSC.GOV.UK: Log4j vulnerability – what everyone needs to know vulnerability 2021