# CVE-2026-118772: joi: quadratic-time split in `string().email({ multiple: true })` allows denial of service

Status: published. Published: 2026-10-29. Updated: 2026-11-04.

joi is a schema description language and data validator for JavaScript. From 17.1.1 until 17.13.9 and 18.3.1, the Joi.string().email({ multiple: true }) rule uses a separator regular expression whose leading whitespace quantifier is retried at every position in a long whitespace run that contains no separator, causing quadratic work during String.prototype.split. The behavior applies to the default separator and every custom separator. Applications that validate attacker-controlled values with the multiple option and no effective prior length limit can have the Node.js event loop blocked for seconds by one request, preventing other work. A .max() rule is not sufficient when abortEarly: false allows the email rule to run after the maximum-length check fails. This vulnerability is fixed in versions 17.13.9 and 18.3.1.

## Remediation

- fix: joi (npm): OSV reports a fixed version 17.13.9. Check the advisory for supported release branches. (source: OSV GHSA-4528-x5fx-h6hg) — https://github.com/advisories/GHSA-4528-x5fx-h6hg
- fix: joi (npm): OSV reports a fixed version 18.3.1. Check the advisory for supported release branches. (source: OSV GHSA-4528-x5fx-h6hg) — https://github.com/advisories/GHSA-4528-x5fx-h6hg

## Affected products and versions

- hapijs / joi: >= 16.0.0, <= 17.1.1 (affected); >= 18.0.0, < 18.3.1 (affected). Source: CNA: GitHub_M
- @hapi / joi: >= 16.0.0, <= 17.1.1 (affected). Source: CNA: GitHub_M
-  / joi (joi): ≥ 17.1.1; < 17.13.9 (affected, semver); OSV events: introduced 17.1.1; fixed 17.13.9. Source: OSV GHSA-4528-x5fx-h6hg
-  / @hapi/joi (@hapi/joi): ≥ 16.0.0; ≤ 17.1.1 (affected, semver); OSV events: introduced 16.0.0; last affected 17.1.1. Source: OSV GHSA-4528-x5fx-h6hg
-  / joi (joi): ≥ 18.0.0; < 18.3.1 (affected, semver); OSV events: introduced 18.0.0; fixed 18.3.1. Source: OSV GHSA-4528-x5fx-h6hg

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: 0.47% as of 2026-11-03; percentile 40.49%

- SSVC: exploitation poc; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-1333

## Exploit evidence

- exploit: https://github.com/hapijs/joi/security/advisories/GHSA-4528-x5fx-h6hg (ADP: CISA-ADP)

## References

- https://github.com/hapijs/joi/security/advisories/GHSA-4528-x5fx-h6hg (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/hapijs/joi/pull/3162 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/hapijs/joi/pull/3163 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/hapijs/joi/commit/03dc1d909818503b06240dadc81e9227ed2649cf (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/hapijs/joi/commit/807858d7480f5075b0610817e3e44230890fb18e (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/hapijs/joi/releases/tag/v17.13.9 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/hapijs/joi/releases/tag/v18.3.1 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/hapijs/joi/security/advisories/GHSA-4528-x5fx-h6hg (ADP: CISA-ADP; exploit)

- https://github.com/advisories/GHSA-4528-x5fx-h6hg (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-4528-x5fx-h6hg (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-118772; retrieved 2026-11-04; source updated 2026-11-04

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-4528-x5fx-h6hg; retrieved 2026-11-04; source updated 2026-10-30

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-118772; retrieved 2026-11-04; source updated Not reported

Revision: 95a0b0749068d5af4224f5fa54735d87bb2978648177ab1db0dcbf630e0876ba

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