Intel has not yet released the details of the vulnerability, but it is believed to affect chips in millions of computers from the last decade.
The UK's National Cyber Security Centre (NCSC) said it was aware of the issue and that patches were being produced.
Some experts said a software fix could slow down computers.
Note: Windows Insiders running Build 17035 already have the fix.
Response from Intel at Intel Responds to Security Research Findings
Recent reports that these exploits are caused by a “bug” or a “flaw” and are unique to Intel products are incorrect. Based on the analysis to date, many types of computing devices — with many different vendors’ processors and operating systems — are susceptible to these exploits.
Intel is committed to product and customer security and is working closely with many other technology companies, including AMD, ARM Holdings and several operating system vendors, to develop an industry-wide approach to resolve this issue promptly and constructively. Intel has begun providing software and firmware updates to mitigate these exploits. Contrary to some reports, any performance impacts are workload-dependent, and, for the average computer user, should not be significant and will be mitigated over time.