{"id":"CVE-2021-23436","aliases":["GHSA-33f9-j839-rf8h"],"url":"https://o3.security/vulnerability/CVE-2021-23436","summary":"Prototype Pollution in immer","details":"This affects the package immer before 9.0.6. A type confusion vulnerability can lead to a bypass of CVE-2020-28477 when the user-provided keys used in the path parameter are arrays. In particular, this bypass is possible because the condition (p === \"__proto__\" || p === \"constructor\") in applyPatches_ returns false if p is ['__proto__'] (or ['constructor']). The === operator (strict equality operator) returns false if the operands have different type.","published":"2021-09-01T18:15:08.477Z","modified":"2026-07-09T05:13:42.070756Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":{"score":0.0178,"percentile":0.76216,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":2,"affectedPackages":[{"ecosystem":"npm","name":"immer","fixedVersion":"9.0.6"}],"fix":{"url":"https://github.com/immerjs/immer/commit/fa671e55ee9bd42ae08cc239102b665a23958237","label":"immerjs/immer@fa671e5"},"references":[{"type":"FIX","url":"https://github.com/immerjs/immer/commit/fa671e55ee9bd42ae08cc239102b665a23958237"},{"type":"FIX","url":"https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579266"},{"type":"FIX","url":"https://snyk.io/vuln/SNYK-JS-IMMER-1540542"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T05:13:42.070756Z"}}