GHSA-834v-8h66-3h79: happy-dom (CVE-2026-115895)

Package	Ecosystem	Affected	Fixed in
happy-dom	npm	>=17.0.0, <21.0.4	21.0.4

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Happy DOM versions from 17.0.0 before 21.0.4 are vulnerable: the ESM compiler inserts unvalidated import alias names into generated JavaScript, so a syntactically invalid import declaration can be turned into executable code. An attacker who can supply module source to an application that evaluates JavaScript through Happy DOM with JavaScript evaluation enabled could run code with the privileges of the host process. Upgrade to happy-dom 21.0.4, which is listed as the fixed version.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
8.8	High	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0047, the 41st percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 13:33 UTC First seen by agentprime
31 Oct 2026, 13:33 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.