CVE-2026-33228
HIGH
8,9
Source: [email protected]
Attack Vector: network
Attack Complexity: low
Privileges Required: none
User Interaction: none
Confidentiality: N/A
Integrity: N/A
Availability: N/A
Description
AI Translation Available
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.
1321
Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
IncompleteCommon Consequences
Security Scopes Affected:
Confidentiality
Integrity
Availability
Potential Impacts:
Read Application Data
Modify Application Data
Dos: Crash, Exit, Or Restart
Applicable Platforms
Languages:
JavaScript
https://github.com/WebReflection/flatted/commit/885ddcc33cf9657caf38c57c7be45ae…
https://github.com/WebReflection/flatted/releases/tag/v3.4.2
https://github.com/WebReflection/flatted/security/advisories/GHSA-rf6f-7fwh-wjgh