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.
References
Configurations
History
23 Mar 2026, 19:14
| Type | Values Removed | Values Added |
|---|---|---|
| CPE | cpe:2.3:a:webreflection:flatted:*:*:*:*:*:node.js:*:* | |
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 9.8 |
| References | () https://github.com/WebReflection/flatted/commit/885ddcc33cf9657caf38c57c7be45ae1c5272802 - Patch | |
| References | () https://github.com/WebReflection/flatted/releases/tag/v3.4.2 - Product | |
| References | () https://github.com/WebReflection/flatted/security/advisories/GHSA-rf6f-7fwh-wjgh - Exploit, Vendor Advisory | |
| First Time |
Webreflection
Webreflection flatted |
20 Mar 2026, 23:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-03-20 23:16
Updated : 2026-03-23 19:14
NVD link : CVE-2026-33228
Mitre link : CVE-2026-33228
CVE.ORG link : CVE-2026-33228
JSON object : View
Products Affected
webreflection
- flatted
CWE
CWE-1321
Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')