vulnerability / NVI-00010724 / Revision 3
Happy DOM: Incomplete fix for CVE-2026-33943: unsanitized import alias leads to host code execution
GitHub lists this reviewed advisory for happy-dom. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
8.8 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
0.473%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.40935. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
happy-dom
source listed>= 17.0.0, <= 21.0.3
## Summary The ESM compiler in `happy-dom@20.14.5` does not validate imported local binding aliases before interpolating them into generated JavaScript. As a result, an invalid ESM import alias can be transformed into a valid JavaScript destructuring default initializer and executed. This appears to be an alternate injection path and incomplete remediation of GHSA-6q6h-j7hj-3r64 / CVE-2026-33943. The previous fix validates `importName` in the local `export { ... }` handler, but the named import handler still places an unvalidated `alias` directly into code context. These issues were confirmed through the public `Window` and `` APIs using the published `happy-dom` npm package. The PoC reaches the Node.js host `process`, obtains `node:fs`, and creates a proof directory on the host filesystem. ## Confirmed affected versions The PoC was directly tested against: - `happy-dom@17.0.0` - `happy-dom@20.0.0` - `happy-dom@20.1.0` - `happy-dom@20.14.5` The same PoC does not trigger on `happy-dom@16.8.1`. The ESM compiler was introduced by commit `7bc831df2`, first released in `v17.0.0`. The vulnerable interpolation remains present through `v20.14.5`, the latest r
happy-dom
source listedSEMVER: introduced 17.0.0; fixed 21.0.4
## Summary The ESM compiler in `happy-dom@20.14.5` does not validate imported local binding aliases before interpolating them into generated JavaScript. As a result, an invalid ESM import alias can be transformed into a valid JavaScript destructuring default initializer and executed. This appears to be an alternate injection path and incomplete remediation of GHSA-6q6h-j7hj-3r64 / CVE-2026-33943. The previous fix validates `importName` in the local `export { ... }` handler, but the named import handler still places an unvalidated `alias` directly into code context. These issues were confirmed through the public `Window` and `` APIs using the published `happy-dom` npm package. The PoC reaches the Node.js host `process`, obtains `node:fs`, and creates a proof directory on the host filesystem. ## Confirmed affected versions The PoC was directly tested against: - `happy-dom@17.0.0` - `happy-dom@20.0.0` - `happy-dom@20.1.0` - `happy-dom@20.14.5` The same PoC does not trigger on `happy-dom@16.8.1`. The ESM compiler was introduced by commit `7bc831df2`, first released in `v17.0.0`. The vulnerable interpolation remains present through `v20.14.5`, the latest r
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
- vendor patch
The original advisory lists fixed boundaries 21.0.4 for happy-dom. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-834v-8h66-3h79 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- GHSA-834v-8h66-3h79 ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
- CVE-2026-115895 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 3 ·
Source facts changed; compare the preserved prior revision.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.