Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:R) | A user must take an action |
| Scope (S:U) | Scope unchanged |
| Confidentiality (C:H) | High confidentiality impact |
| Integrity (I:H) | High integrity impact |
| Availability (A:H) | High availability impact |
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
About Capricorn86 Happy Dom
CVE-2026-33943 affects Capricorn86 Happy Dom, a product from Capricorn86. Before acting, confirm where Capricorn86 Happy Dom runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. In versions 15.10.0 through 20.8.7, a code injection vulnerability in `ECMAScriptModuleCompiler` allows an attacker to achieve Remote Code Execution (RCE) by injecting arbitrary JavaScript expressions inside `export { }` declarations in ES module scripts processed by happy-dom. The compiler directly interpolates unsanitized content into generated code as an executable expression, and the quote filter does not strip backticks, allowing template literal-based payloads to bypass sanitization. Version 20.8.8 fixes the issue.
The weakness class is Code Injection. Attacker input is executed as program code.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and relies on a user taking an action. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Capricorn86 Happy Dom |
| Affected versions | Happy Dom from 15.10.0 before 20.8.8 |
| Published | Mar 27, 2026 |
| Last modified | Jul 15, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | security-advisories@github.com |
How to detect it
- Inventory every instance of Capricorn86 Happy Dom and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Capricorn86 Happy Dom named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Capricorn86 Happy Dom to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-94: Code Injection More CVEs with this weakness
- CWE-917 More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
Autel Maxi Charger Single firmware through V1.03.51 allows unauthenticated remote code execution via the service listening on TCP port 9002. A crafted request to the /test endpoint can cause the device to download, extract, and execute attacker-controlled files with root privileges.
Erugo is a self-hosted file-sharing platform. In versions up to and including 0.2.14, an authenticated low-privileged user can upload arbitrary files to any specified location due to insufficient validation of user‑supplied paths when creating shares. By specifying a writable path within the public web root, an attacker can upload and execute arbitrary code on the server, resulting in remote code execution (RCE). This vulnerability allows a low-privileged user to fully compromise the affected Erugo instance. Version 0.2.15 fixes the issue.
Postiz is an AI social media scheduling tool. Prior to commit da44801, a "Pwn Request" vulnerability in the Build and Publish PR Docker Image workflow (.github/workflows/pr-docker-build.yml) allows any unauthenticated user to execute arbitrary code during the Docker build process and exfiltrate a highly privileged GITHUB_TOKEN (write-all permissions). This can be achieved simply by opening a Pull Request from a fork with a maliciously modified Dockerfile.dev. This issue has been patched via commit da44801.
CI4MS is a CodeIgniter 4-based CMS skeleton that delivers a production-ready, modular architecture with RBAC authorization and theme support. Prior to version 0.28.5.0, an authenticated user with file editor permissions can achieve Remote Code Execution (RCE) by leveraging the file creation and save endpoints, an attacker can upload and execute arbitrary PHP code on the server. This issue has been patched in version 0.28.5.0.
Budibase is a low code platform for creating internal tools, workflows, and admin panels. Prior to version 3.30.4, an unsafe `eval()` vulnerability in Budibase's view filtering implementation allows any authenticated user (including free tier accounts) to execute arbitrary JavaScript code on the server. This vulnerability ONLY affects Budibase Cloud (SaaS) - self-hosted deployments use native CouchDB views and are not vulnerable. The vulnerability exists in `packages/server/src/db/inMemoryView.ts` where user-controlled view map functions are directly evaluated without sanitization. The primary impact comes from what lives inside the pod's environment: the `app-service` pod runs with secrets baked into its environment variables, including `INTERNAL_API_KEY`, `JWT_SECRET`, CouchDB admin credentials, AWS keys, and more. Using the extracted CouchDB credentials, we verified direct database access, enumerated all tenant databases, and confirmed that user records (email addresses) are readable. Version 3.30.4 contains a patch.
Adobe Campaign Classic (ACC) is affected by an Improper Control of Generation of Code ('Code Injection') vulnerability that could result in arbitrary code execution in the context of the current user. A low-privileged attacker could exploit this vulnerability to execute arbitrary code. Exploitation of this issue does not require user interaction. Scope is changed.
Earn your free CTEM certification.
Learn to scope, prioritize, validate and mobilize fixes for CVEs like CVE-2026-33943 with a free CTEM certification.
Beginner / Practitioner / Program Leader
Explore certifications