CVE-2026-33943
RCE in Happy DOM via unsanitized ES module export in ECMAScriptModuleCompiler
Is CVE-2026-33943 being exploited?
Not confirmed. CVE-2026-33943 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.79% probability of exploitation in the next 30 days.
How severe is CVE-2026-33943?
CVE-2026-33943 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-33943?
Yes. A fix has been recorded for CVE-2026-33943. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-33943 affect?
CVE-2026-33943 affects Happy DOM 15.10.0–20.8.7 (ECMAScriptModuleCompiler). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-33943?
Upgrade to Happy DOM 20.8.8+ immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution via crafted ES module export expressions; unsanitized payloads executed by compiler.
Patch when possible
- affected>= 15.10.0 and < 20.8.8
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.