Related Vulnerabilities: CVE-2019-9791  

The type inference system in Firefox before 66.0 allows the compilation of functions that can cause type confusions between arbitrary objects when compiled through the IonMonkey just-in-time (JIT) compiler and when the constructor function is entered through on-stack replacement (OSR). This allows for possible arbitrary reading and writing of objects during an exploitable crash.

Severity Critical

Remote Yes

Type Arbitrary code execution

Description

The type inference system in Firefox before 66.0 allows the compilation of functions that can cause type confusions between arbitrary objects when compiled through the IonMonkey just-in-time (JIT) compiler and when the constructor function is entered through on-stack replacement (OSR). This allows for possible arbitrary reading and writing of objects during an exploitable crash.

AVG-925 firefox 65.0.2-1 66.0-1 Critical Fixed

https://www.mozilla.org/en-US/security/advisories/mfsa2019-07/#CVE-2019-9791
https://bugzilla.mozilla.org/show_bug.cgi?id=1530958