{"id":"GHSA-gcqx-w48m-w2h4","summary":"deepmerge mergeObject() allows prototype poisoning of returned objects","details":"deepmerge through 4.3.1 contains a prototype poisoning vulnerability in the mergeObject() function that fails to properly validate keys being written to target objects. Attackers can supply malicious source objects in merge operations to inject attacker-controlled properties into the returned object's prototype, causing applications to inherit unintended values when accessing properties without own-property checks.","aliases":["CVE-2026-93753"],"modified":"2026-10-27T21:45:04.256048049Z","published":"2026-09-18T18:31:44Z","database_specific":{"severity":"LOW","github_reviewed":true,"github_reviewed_at":"2026-10-27T21:34:55Z","nvd_published_at":"2026-09-18T18:18:34Z","cwe_ids":["CWE-1321"]},"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93753"},{"type":"WEB","url":"https://github.com/TehShrike/deepmerge/issues/273"},{"type":"PACKAGE","url":"https://github.com/TehShrike/deepmerge"},{"type":"WEB","url":"https://github.com/TehShrike/deepmerge/blob/5b87756a5671635679001cbac72aa42f23472c81/index.js#L39-L60"},{"type":"WEB","url":"https://www.vulncheck.com/advisories/deepmerge-through-4.3.1-prototype-poisoning-via-mergeobject"}],"affected":[{"package":{"name":"deepmerge","ecosystem":"npm","purl":"pkg:npm/deepmerge"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.2.0"},{"last_affected":"4.3.1"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-gcqx-w48m-w2h4/GHSA-gcqx-w48m-w2h4.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U"}]}