GHSA-gg4h-3hg2-grpc
joi: object().rename() with a template target can set the validated object's prototype
Packages
Details
As written in the advisory (Markdown source, shown as plain text).
### Impact
Applications 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-(.+)$/, Joi.x('{#1}'), { multiple: true })`. Because the target is rendered from the matched input key, an attacker who controls input keys can send `x-__proto__` with an object value and make the rename target render as `__proto__`, which sets the prototype of the object joi returns instead of creating a key on it. The global `Object.prototype` is not modified, so the effect is confined to the object returned by that one `validate()` call.
Schemas using a static string rename target are not affected, and neither are schemas left on the default `{ multiple: false }`.
### Patches
Versions 17.13.5 and 18.2.4 have been released to address the issue.
### Workarounds
1. Replace the template rename target with a static string target.
2. Keep the template but make the capture unable to produce `__proto__`, using a negative lookahead: `.rename(/^x-(?!__proto__$)(.+)$/, Joi.x('{#1}'), { multiple: true })`
3. Drop { multiple: true } from the rename, which stops the rename before the assignment.
References
External links from the advisory. They lead to third-party sites.
- https://github.com/hapijs/joi/security/advisories/GHSA-gg4h-3hg2-grpc
- https://nvd.nist.gov/vuln/detail/CVE-2026-84367
- https://github.com/hapijs/joi/pull/3134
- https://github.com/hapijs/joi/pull/3135
- https://github.com/hapijs/joi/commit/162f367aa178d2e1ebec8dc1164e5fe16536ddf6
- https://github.com/hapijs/joi/commit/172ececa192feda532b743d77bc9d3e523d19b01
- https://github.com/hapijs/joi
- https://github.com/hapijs/joi/releases/tag/v17.13.5
- https://github.com/hapijs/joi/releases/tag/v18.2.4