# CVE-2026-118661: Happy DOM: Cookie scope forgery: no DNS-label boundary on Domain= matching , attacker origin sets victim cookies


- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** GHSA-5fpq-26gf-qwcr

## What is CVE-2026-118661?

CVE-2026-118661 is a medium-severity vulnerability in capricorn86 happy-dom, published on 28 Oct 2026. 

### 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.

Weakness: CWE-565 (Reliance on Cookies without Validation and Integrity Checking)

## Which versions are affected by CVE-2026-118661?

2 open source packages ship an affected version, including happy-dom.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `happy-dom` | npm | All versions | 20.14.6 |
| `happy-dom` | npm | All versions | 20.14.6 |

## How do I fix CVE-2026-118661?

Upgrade happy-dom to 20.14.6 or later.

## Is CVE-2026-118661 being exploited?

There is no known exploitation of CVE-2026-118661 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-118661 and fix it if it is affected.

What it is: CVE-2026-118661 is a medium-severity vulnerability in capricorn86 happy-dom, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-118661 in the wild and no public exploit code.

Affected packages and fixed versions:
- happy-dom (npm): affected all versions; fixed in 20.14.6
- happy-dom (npm): affected all versions; fixed in 20.14.6

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-118661/ (Markdown: https://insights.sbomify.com/CVE-2026-118661/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-118661
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-118661
- OSV: https://osv.dev/vulnerability/CVE-2026-118661

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-118661/
Summaries are generated and may contain mistakes; the official description above is the record.