What is CVE-2026-118661?

CVE-2026-118661 is a medium-severity vulnerability in Capricorn86 Happy-Dom, classified under Reliance on Cookies without Validation and Integrity Checking. CVSS score: 6.5/10. Published 2026-10-28.

How severe is CVE-2026-118661?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Capricorn86 Happy-Dom

CVE-2026-118661

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.

Published 2026-10-28.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Capricorn86 Happy-Dom — versions < 20.14.6

Weakness classification (CWE)

CWE-565 — Reliance on Cookies without Validation and Integrity Checking

References

Frequently asked questions

What is CVE-2026-118661?: CVE-2026-118661 is a medium-severity vulnerability in Capricorn86 Happy-Dom, classified under Reliance on Cookies without Validation and Integrity Checking. CVSS score: 6.5/10. Published 2026-10-28.
How severe is CVE-2026-118661?: Medium severity. CVSS v3 base score is 6.5 out of 10.