{"id":"GHSA-8hq9-phh3-p2wp","summary":"Elysia Cookie Value Prototype Pollution","details":"### Impact\nElysia cookie can be overridden by prototype pollution , eg. `__proto__`\n\nSending cookie with the follows name can override cookie value:\n```bash\n__proto__=%7B%22injected%22%3A%22polluted%22%7D\n```\n\n### Patches\nPatched by 1.4.27\n\n### Workarounds\n1. Use t.Cookie validation to enforce validation value\n2. Prevent iterable over cookie if possible","aliases":["CVE-2026-31865"],"modified":"2026-03-19T19:17:47.117772Z","published":"2026-03-17T16:17:41Z","database_specific":{"github_reviewed_at":"2026-03-17T16:17:41Z","nvd_published_at":"2026-03-18T04:17:19Z","cwe_ids":["CWE-1321"],"severity":"MODERATE","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/elysiajs/elysia/security/advisories/GHSA-8hq9-phh3-p2wp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31865"},{"type":"WEB","url":"https://github.com/elysiajs/elysia/commit/e9d6b1743fa7368ef942dce181f6a089757f6aab"},{"type":"PACKAGE","url":"https://github.com/elysiajs/elysia"}],"affected":[{"package":{"name":"elysia","ecosystem":"npm","purl":"pkg:npm/elysia"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.4.27"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-8hq9-phh3-p2wp/GHSA-8hq9-phh3-p2wp.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"}]}