Vulnerability · Published Oct 28, 2026 · Assigned by GitHub_M
CVE-2026-118661Happy DOM: Cookie scope forgery: no DNS-label boundary on Domain= matching , attacker origin sets victim cookies
Medium 6.5
In plain English
A medium-severity security flaw in happy-dom from capricorn86. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. Prior to 20.14.6, Happy DOM's CookieContainer in src/cookie/CookieContainer.ts does not correctly validate or match Domain cookie attributes. It can accept a Domain unrelated to the origin setting the cookie, including a public suffix, and separately treats an unrelated suffix-sharing hostname as a match because cookieMatchesURL does not enforce a DNS-label boundary. In server-side rendering and prerendering applications that contact attacker-controlled origins and then make requests to a victim origin, these behaviors can plant and deliver a forged cookie, enabling cookie injection or session fixation. This issue is fixed in version 20.14.6.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | happy-dom | 20.14.6 | GHSA-5fpq-26gf-qwcr |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| capricorn86 | happy-dom | < 20.14.6 |
Weakness: CWE-565 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
References
- https://github.com/capricorn86/happy-dom/security/advisories/GHSA-5fpq-26gf-qwcr x_refsource_CONFIRM
- https://github.com/capricorn86/happy-dom/pull/2477 x_refsource_MISC
- https://github.com/capricorn86/happy-dom/commit/f21dbd7d0a0c63cdd41954ba5d0f05def4e0f2b3 x_refsource_MISC
- https://github.com/capricorn86/happy-dom/releases/tag/v20.14.6 x_refsource_MISC