{"id":"GHSA-gcqx-w48m-w2h4","aliases":["CVE-2026-93753"],"title":"deepmerge mergeObject() allows prototype poisoning of returned objects","titleSource":"OSV","descriptionSource":"OSV","declaredSeverity":"LOW","description":"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checks.","severity":"medium","score":5.3,"published":"2026-09-18T18:31:44.000Z","modified":"2026-10-27T21:45:04.256Z","withdrawn":false,"knownExploited":false,"affected":[{"ecosystem":"npm","name":"deepmerge","sources":[{"name":"OSV · GHSA-gcqx-w48m-w2h4","url":"https://osv.dev/vulnerability/GHSA-gcqx-w48m-w2h4"}],"ranges":[{"events":[{"introduced":"4.2.0"},{"last_affected":"4.3.1"}],"type":"SEMVER"}],"versions":[],"fixed":[]}],"sourceAffected":[],"references":["https://nvd.nist.gov/vuln/detail/CVE-2026-93753","https://github.com/TehShrike/deepmerge/issues/273","https://github.com/TehShrike/deepmerge","https://github.com/TehShrike/deepmerge/blob/5b87756a5671635679001cbac72aa42f23472c81/index.js#L39-L60","https://www.vulncheck.com/advisories/deepmerge-through-4.3.1-prototype-poisoning-via-mergeobject"],"sources":[{"name":"OSV","id":"GHSA-gcqx-w48m-w2h4","modified":"2026-10-27T21:45:04.256048049Z","url":"https://osv.dev/vulnerability/GHSA-gcqx-w48m-w2h4"}],"assessments":[{"source":"OSV","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3},{"source":"OSV","vector":"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","score":2.7}],"products":[],"remediation":[],"kev":{"status":"not-listed","checkedAt":"2026-10-28T12:35:32.459Z"},"coverage":[{"source":"NVD","status":"not-checked"},{"source":"GHSA","status":"not-checked"},{"source":"EUVD","status":"not-checked"},{"source":"EPSS","status":"not-checked"}],"evidence":[]}