Mozilla has released critical security updates for Firefox and Firefox ESR on Friday, patching two vulnerabilities that are being actively exploited by attackers.
fixed in Firefox 74.0.1 and Firefox ESR 68.6.1 are:
- CVE-2020-6819: A use-after-free flaw caused by a race condition while running the nsDocShell destructor
- CVE-2020-6820: A use-after-free caused by a race condition when handling a ReadableStream
No additional details about them have been provided and the bug entries in Mozilla’s bug database are still unaccessible to the wider public. The bugs have been rated “critical”, which means that chances are high they can lead to remote code execution (whether individually or concatenated together).
The vulnerabilities (and presumably their active exploitation) have been flagged by security researchers Francisco Alonso and Javier Marcos.
One of Alonso’s comments on Twitter seems to indicate that the flaws may also affect other browsers: