{"id":"CVE-2026-84367","aliases":["GHSA-gg4h-3hg2-grpc"],"url":"https://o3.security/vulnerability/CVE-2026-84367","summary":"joi: object().rename() with a template target can set the validated object's prototype","details":"### Impact\n\nApplications are affected only if a schema renames keys with a regular-expression source and a `Joi.expression()` / `Joi.x()` target that interpolates the pattern's own match data, combined with `{ multiple: true }`, for example `.rename(/^x-(.+)$/, Joi.x('{#1}'), { multiple: true })`. Because the target is rendered from the matched input key, an attacker who controls input keys can send `x-__proto__` with an object value and make the rename target render as `__proto__`, which sets the prototype of the object joi returns instead of creating a key on it. The global `Object.prototype` is not modified, so the effect is confined to the object returned by that one `validate()` call.\n\nSchemas using a static string rename target are not affected, and neither are schemas left on the default `{ multiple: false }`.\n\n### Patches\n\nVersions 17.13.5 and 18.2.4 have been released to address the issue.\n\n### Workarounds\n\n1. Replace the template rename target with a static string target.\n2. Keep the template but make the capture unable to produce `__proto__`, using a negative lookahead: `.rename(/^x-(?!__proto__$)(.+)$/, Joi.x('{#1}'), { multiple: true })`\n3. Drop { multiple: true } from the rename, which stops the rename before the assignment.","published":"2026-09-01T20:33:29.295Z","modified":"2026-10-21T03:00:29.112472038Z","cvss":{"score":3.7,"severity":"LOW","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"},"epss":{"score":0.0027,"percentile":0.19296,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"joi","fixedVersion":"17.13.5"},{"ecosystem":"npm","name":"joi","fixedVersion":"18.2.4"}],"fix":{"url":"https://github.com/hapijs/joi/commit/162f367aa178d2e1ebec8dc1164e5fe16536ddf6","label":"hapijs/joi@162f367"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84367.json"},{"type":"ADVISORY","url":"https://github.com/hapijs/joi/security/advisories/GHSA-gg4h-3hg2-grpc"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-84367"},{"type":"FIX","url":"https://github.com/hapijs/joi/commit/162f367aa178d2e1ebec8dc1164e5fe16536ddf6"},{"type":"FIX","url":"https://github.com/hapijs/joi/commit/172ececa192feda532b743d77bc9d3e523d19b01"},{"type":"FIX","url":"https://github.com/hapijs/joi/pull/3134"},{"type":"FIX","url":"https://github.com/hapijs/joi/pull/3135"},{"type":"PACKAGE","url":"https://github.com/hapijs/joi"},{"type":"WEB","url":"https://github.com/hapijs/joi/releases/tag/v17.13.5"},{"type":"WEB","url":"https://github.com/hapijs/joi/releases/tag/v18.2.4"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T03:00:29.112472038Z"}}