{"id":"CVE-2026-33228","revision":"d84fd50e77754ee285e207c9abfebc3c","records":[{"revision":"d84fd50e77754ee285e207c9abfebc3c","observedAt":"2026-10-25T08:17:18.375+00:00","statement":{"source":"nvd","id":"CVE-2026-33228","aliases":[],"title":"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 intern…","description":"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.","state":0,"publishedAt":"2026-03-20T23:16:46.51+00:00","modifiedAt":"2026-09-04T13:18:55.12+00:00","affected":[],"metrics":[{"system":"CVSS 4.0 · security-advisories@github.com · Secondary","vector":"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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","score":8.9,"severity":"HIGH"},{"system":"CVSS 3.1 · nvd@nist.gov · Primary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"},{"system":"CVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://github.com/WebReflection/flatted/commit/885ddcc33cf9657caf38c57c7be45ae1c5272802","https://github.com/WebReflection/flatted/releases/tag/v3.4.2","https://github.com/WebReflection/flatted/security/advisories/GHSA-rf6f-7fwh-wjgh","https://access.redhat.com/errata/RHSA-2026:13826","https://access.redhat.com/errata/RHSA-2026:34342","https://access.redhat.com/errata/RHSA-2026:9742","https://access.redhat.com/security/cve/CVE-2026-33228","https://bugzilla.redhat.com/show_bug.cgi?id=2449872","https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33228.json"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-33228","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Modified","weaknesses":["CWE-1321","CWE-915"],"productCriteria":["cpe:2.3:a:webreflection:flatted:*:*:*:*:*:node.js:*:*"],"sourceDates":{"published":"2026-03-20T23:16:46.510","lastModified":"2026-09-04T13:18:55.120"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-33228","identifiers":["CVE-2026-33228"]},"retained":false,"historicalAffected":[]}],"coverage":[]}