View at Official debian advisory, NVD, CVE.org · CVE detail
Freshness: upstream tracker timestamp is available; use API updated time as primary recency signal.
CVE-2026-33228 not yet assigned priority: Debian including 1 source packages (node-flatted), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 3, open 2.
flatted is a circular JSON parser. Prior to version 3.4.2, the parse() function in flatted can use attacker-controlled string values from the parsed JSON as direct array index keys, without validating that they are numeric. Since the internal input buffer is a JavaScript Array, accessing it with the key "__proto__" returns Array.prototype via the inherited getter. This object is then treated as a legitimate parsed value and assigned as a property of the output object, effectively leaking a live reference to Array.prototype to the consumer. Any code that subsequently writes to that property will pollute the global prototype. This issue has been patched in version 3.4.2.