CVE-2026-84367: Prototype Pollution (CVSS 3.7)

Description

joi is a schema description language and data validator for JavaScript. From 16.0.0 until 17.13.5 and 18.2.4, joi's lib/types/keys.js internals.rename() implementation used by object().rename() permits a schema that renames keys with a regular-expression source and a Joi.expression() or Joi.x() target that interpolates the pattern's own match data, combined with { multiple: true }, to derive a target from an attacker-controlled input key. An attacker can send x-__proto__ with an object value, causing the target to render as __proto__ and set the prototype of the object returned by validate() instead of creating an own key. The global Object.prototype is not modified, so the effect is confined to the object returned by that validation call. Static-string targets and schemas using the default { multiple: false } are not affected. This issue is fixed in versions 17.13.5 and 18.2.4.

Is your site exposed to CVE-2026-84367?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

3.7

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0027

Probability of exploitation

0.19%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-1321 CWE-1321

References

Other References

https://github.com/hapijs/joi/commit/162f367aa178d2e1ebec8dc1164e5fe16536ddf6 https://github.com/hapijs/joi/commit/172ececa192feda532b743d77bc9d3e523d19b01 https://github.com/hapijs/joi/pull/3134 https://github.com/hapijs/joi/pull/3135 https://github.com/hapijs/joi/security/advisories/GHSA-gg4h-3hg2-grpc

Frequently Asked Questions

What is CVE-2026-84367? +

joi is a schema description language and data validator for JavaScript. From 16.0.0 until 17.13.5 and 18.2.4, joi's lib/types/keys.js internals.rename() implementation used by object().rename() permits a schema that renames keys with a regular-expression source and a Joi.expression() or Joi.x() target that interpolates the pattern's own match data, combined with { multiple: true }, to derive a target from an attacker-controlled input key. An attacker can send x-__proto__ with an object value, causing the target to render as __proto__ and set the prototype of the object returned by validate() instead of creating an own key. The global Object.prototype is not modified, so the effect is confined to the object returned by that validation call. Static-string targets and schemas using the default { multiple: false } are not affected. This issue is fixed in versions 17.13.5 and 18.2.4. It has a CVSS v3.1 base score of 3.7 (LOW).

How severe is CVE-2026-84367? +

CVE-2026-84367 has a CVSS v3.1 score of 3.7 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0027, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-84367? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-27597

Vue I18n is the internationalization plugin for Vue.js. @intlify/message-resolver and @intlify/vue-i18n-core are vulnerable to Prototype Pollution through the entry function: …

CVE-2025-32014

estree-util-value-to-estree converts a JavaScript value to an ESTree expression. When generating an ESTree from a value with a property named …

CVE-2025-48054

Radashi is a TypeScript utility toolkit. Prior to version 12.5.1, the set function within the Radashi library is vulnerable to …

CVE-2025-8101

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability in Linkify (linkifyjs) allows XSS Targeting HTML Attributes and Manipulating …

CVE-2025-34146

A prototype pollution vulnerability exists in @nyariv/sandboxjs versions <= 0.8.23, allowing attackers to inject arbitrary properties into Object.prototype via crafted …

CVE-2025-55164

content-security-policy-parser parses content security policy directives. A prototype pollution vulnerability exists in versions 0.5.0 and earlier, wherein if a policy …

CVE-2026-84367