Array index error in the scanstring function in the _json module in Python 2.7 through 3.5 and simplejson before 2.6.1 allows context-dependent attackers to read arbitrary process memory via a negative index value in the idx argument to the raw_decode function.

The is-my-json-valid package before 2.12.4 for Node.js has an incorrect exports['utc-millisec'] regular expression, which allows remote attackers to cause a denial of service (blocked event loop) via a crafted string.

The extractFrom function in Internals/QuotedString.cpp in Arduino JSON before 4.5 allows remote attackers to cause a denial of service (crash) via a JSON string with a \ (backslash) followed by a terminator, as demonstrated by "\\\0", which triggers a buffer overflow and over-read.