bson before 0.8 incorrectly uses int rather than sizet for many variables, parameters, and return values. In particular, the bsonensure_space() parameter bytesNeeded could have an integer overflow via properly constructed bson input.
{ "urgency": "unimportant" }
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2020-12135.json"