Vulnerability · Published Oct 28, 2026 · Assigned by GitHub_M

CVE-2026-118659@happy-dom/server-renderer: ServerRendererServer Target-Origin Bypass SSRF / Open Proxy

High 7.5

In plain English

A high-severity server-side request forgery 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 0.4% (higher than 33% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.4%top 66.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. Prior to 21.0.2, the Happy DOM server-renderer package's ServerRendererServer accepts unauthenticated HTTP/2 requests and resolves attacker-controlled :path values against server.targetOrigin in #onIncomingRequest in packages/@happy-dom/server-renderer/src/ServerRendererServer.ts without confirming that the resolved origin remains trusted before calling fetch. A protocol-relative path can change the destination to an arbitrary HTTP or HTTPS endpoint reachable by the server, including local and internal services, and the proxy relays the fetched response headers and body to the requester. This issue is fixed in version 21.0.2.

Affected products (as reported)

Vendor	Product	Versions
capricorn86	happy-dom	< 21.0.2

Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

https://github.com/capricorn86/happy-dom/security/advisories/GHSA-pmf4-3xr3-xjhg x_refsource_CONFIRM
https://github.com/capricorn86/happy-dom/pull/2520 x_refsource_MISC
https://github.com/capricorn86/happy-dom/commit/1f3ffdf634231361de1a2acb629b4fe8ee1bd85d x_refsource_MISC
https://github.com/capricorn86/happy-dom/releases/tag/v21.0.2 x_refsource_MISC