{"id":"DEBIAN-CVE-2026-33228","details":"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.","modified":"2026-09-05T08:47:35.347370555Z","published":"2026-03-20T23:16:46.510Z","upstream":["CVE-2026-33228"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-33228"}],"affected":[{"package":{"name":"node-flatted","ecosystem":"Debian:12","purl":"pkg:deb/debian/node-flatted?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.2.7~ds-1","3.2.7~ds-1+deb12u1","3.4.1~ds-1","3.4.2~ds-1","3.4.4~ds-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33228.json"}},{"package":{"name":"node-flatted","ecosystem":"Debian:13","purl":"pkg:deb/debian/node-flatted?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.2.7~ds-1+deb13u1"}]}],"versions":["3.2.7~ds-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33228.json"}},{"package":{"name":"node-flatted","ecosystem":"Debian:14","purl":"pkg:deb/debian/node-flatted?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.4.2~ds-1"}]}],"versions":["3.2.7~ds-1","3.4.1~ds-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-33228.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}