CVE-2020-1913: 
JavaScript vulnerability analysis and mitigation

CVE-2020-1913 is an Integer signedness error vulnerability discovered in the JavaScript Interpreter of Facebook Hermes prior to commit 2c7af7ec481ceffd0d14ce2d7c045e475fd71dc6. The vulnerability was disclosed on September 9, 2020 (NVD).

The vulnerability stems from an incorrect type usage in the SwitchImm implementation where the offset was being read from a uint32_t * instead of int32_t *. This improper handling of signed integers in backward branching operations could lead to potential security issues (Github Commit).

The incorrect handling of signed integers in the JavaScript interpreter could potentially lead to memory corruption or other undefined behavior when processing switch statements with backward branches.

The vulnerability requires the execution of JavaScript code containing specific switch statement patterns that trigger backward branching in the Hermes JavaScript engine.

The issue was fixed in commit 2c7af7ec481ceffd0d14ce2d7c045e475fd71dc6 by changing the pointer type from uint32_t * to int32_t * to properly handle signed offsets in backward branching operations (Github Commit).