Security readout for executives and security teams
Plain-English summary
Happy DOM versions 15.10.0 through 20.8.7 can turn a malicious ES module export declaration into executable JavaScript. If an application processes attacker-controlled module scripts with happy-dom, this can lead to remote code execution. Version 20.8.8 fixes the issue.
Executive priority
Treat as urgent where happy-dom processes untrusted scripts, because successful exploitation could compromise host confidentiality, integrity, and availability. Lower priority where happy-dom is only isolated test tooling.
Technical view
The ECMAScriptModuleCompiler interpolates unsanitized export names into generated code. The described quote filtering misses backticks, so template literal syntax can bypass sanitization and execute injected expressions. The affected package range is capricorn86 happy-dom >=15.10.0 and <20.8.8.
Likely exposure
Exposure is most likely in server-side JavaScript, test, scraping, rendering, or automation workflows that use happy-dom to process untrusted or user-supplied ES module scripts.
Exploitation context
The source bundle reports RCE potential but does not cite active exploitation. KEV is false. The CVSS vector shows network attackability, low complexity, no privileges, and user interaction required.
Researcher notes
The advisory identifies the vulnerable compiler component, affected range, CWE-917 and CWE-94 classifications, and fixed release. Evidence provided does not establish real-world exploitation or affected downstream applications.
Mitigation direction
- Upgrade happy-dom to version 20.8.8 or later.
- Regenerate and redeploy lockfiles after upgrading the dependency.
- Avoid processing untrusted ES module scripts with vulnerable happy-dom versions.
- Check vendor and distribution guidance for downstream package status.
Validation and detection
- Search SBOMs and lockfiles for happy-dom versions below 20.8.8.
- Map happy-dom usage to any user-supplied script processing paths.
- Confirm production artifacts contain happy-dom 20.8.8 or later.
- Run dependency scanning after lockfile updates.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-917: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-94: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-33943 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
2 official scoresWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9GitHub_MCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H2.85.9redhat-SADPVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-03-27T22:02:46.904Z: Reported to Red Hat.
- 2026-03-27T21:15:19.186Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64CVE reference, GitHub_M · x_refsource_CONFIRM
- https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3cCVE reference, GitHub_M · x_refsource_MISC
- https://github.com/capricorn86/happy-dom/releases/tag/v20.8.8CVE reference, GitHub_M · x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-33943CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2452522CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33943.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')
Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improper Control of Generation of Code ('Code Injection')
Improper Control of Generation of Code ('Code Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.