CVE-2026-84368
joi: Prototype pollution via a `__proto__` language key in custom messages
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
joi is a schema description language and data validator for JavaScript. From 16.0.0 until 17.13.6 and 18.2.5, the @hapi/joi package through 17.1.1 and the successor joi package contain prototype pollution in lib/messages.js, where exports.compile() and exports.merge() reuse inherited objects for attacker-controlled language keys supplied through messages(), message(), prefs({ messages }), Joi.extend({ messages }), or rule({ message }). A language key named __proto__ writes properties onto Object.prototype, and constructor writes to the Object function's static properties. A consuming application that gates on the presence of an inherited property can take the wrong branch for every inspected object. The flaw is not reachable from data that joi validates and requires an application to feed untrusted input directly into schema-construction configuration. This issue is fixed in joi versions 17.13.6 and 18.2.5; no fixed @hapi/joi version is available.
Timeline
ID reserved
By GitHub_M
Published
- 1 day later
· 1 day later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Low3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
| NVDNVD · Deferred | 3.1 | Low3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.39% · top 67% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 3.7.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
References (5)
- https://github.com/hapijs/joi/security/advisories/GHSA-6w3j-5fw6-r9vr (opens in a new tab)x_refsource_CONFIRM
- https://github.com/hapijs/joi/pull/3138 (opens in a new tab)x_refsource_MISC
- https://github.com/hapijs/joi/pull/3139 (opens in a new tab)x_refsource_MISC
- https://github.com/hapijs/joi/commit/8d0b808f3e874d28f9078f61b7742290989afb36 (opens in a new tab)x_refsource_MISC
- https://github.com/hapijs/joi/commit/90d07571923c90e3432a328fc041d1cda03d30fa (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-6w3j-5fw6-r9vr (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-84368)Record last updated .