{"id":"UBUNTU-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":"2026-06-29T13:50:10.316427973Z","published":"2026-03-20T23:16:00Z","upstream":["CVE-2026-33228"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-33228"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-33228"},{"type":"REPORT","url":"https://github.com/WebReflection/flatted/commit/885ddcc33cf9657caf38c57c7be45ae1c5272802"},{"type":"REPORT","url":"https://github.com/WebReflection/flatted/releases/tag/v3.4.2"},{"type":"REPORT","url":"https://github.com/WebReflection/flatted/security/advisories/GHSA-rf6f-7fwh-wjgh"}],"affected":[{"package":{"name":"node-flatted","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/node-flatted?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.1~dfsg-3","2.0.1~dfsg-4"],"ecosystem_specific":{"binaries":[{"binary_name":"libjs-flatted","binary_version":"2.0.1~dfsg-4"},{"binary_name":"node-flatted","binary_version":"2.0.1~dfsg-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33228.json"}},{"package":{"name":"node-flatted","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/node-flatted?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.2~dfsg-1","2.0.2~dfsg-4","3.2.2~ds-2","3.2.2~ds-3","3.2.4~ds-1","3.2.5~ds-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.2.5~ds-1","binary_name":"libjs-flatted"},{"binary_name":"node-flatted","binary_version":"3.2.5~ds-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33228.json"}},{"package":{"name":"node-flatted","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/node-flatted?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.2.7~ds-1"],"ecosystem_specific":{"binaries":[{"binary_name":"libjs-flatted","binary_version":"3.2.7~ds-1"},{"binary_name":"node-flatted","binary_version":"3.2.7~ds-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33228.json"}},{"package":{"name":"node-flatted","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/node-flatted?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.2.7~ds-1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.2.7~ds-1","binary_name":"libjs-flatted"},{"binary_version":"3.2.7~ds-1","binary_name":"node-flatted"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33228.json"}},{"package":{"name":"node-flatted","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/node-flatted?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.2.7~ds-1","3.4.2~ds-1"],"ecosystem_specific":{"binaries":[{"binary_name":"libjs-flatted","binary_version":"3.4.2~ds-1"},{"binary_name":"node-flatted","binary_version":"3.4.2~ds-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33228.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}