# CVE-2026-118492: Eclipse Langium langium-sprotty XSS in diagnostic messages

Source: https://junglewise.ai/threats/cve-2026-118492-in-eclipse-langium-versions-3-0-0-and-later-the-langium-sprotty  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-09. Updated: 2026-11-09  
License: CC BY 4.0 with a link back

CVE-2026-118492 · Severity: info · Published 2026-11-09

Eclipse Langium is a language engineering framework used to build domain-specific languages and their tooling. The langium-sprotty package fails to sanitize diagnostic error messages before displaying them in hover popups, allowing attackers to inject malicious JavaScript that executes when users view errors in a Sprotty diagram editor. An attacker can craft a source file that triggers an unresolved cross-reference with JavaScript code, which runs when a developer hovers over the error.

Vendors: [Eclipse](https://junglewise.ai/threats/vendors/eclipse).

## Quick answers

**Is CVE-2026-118492 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-118492 being exploited in the wild.

**How severe is CVE-2026-118492?** Informational severity, published 9 November 2026.

**Which products and versions are affected?** Eclipse Langium 3.0.0 and later.

**Is there a fix for CVE-2026-118492?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-118492 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-118492?** Check whether you run Eclipse Langium at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The langium-sprotty package does not HTML-escape diagnostic messages rendered by the `addHoverPopupHandler` function. If a grammar permits cross-reference text to include HTML markup (e.g., via a STRING terminal), an unresolved cross-reference generates a diagnostic containing unescaped attacker-supplied text. When a user hovers over the error marker in a Sprotty diagram, the injected JavaScript executes in the browser or webview context, enabling arbitrary code execution.

## Affected products

- Eclipse Langium 3.0.0 and later

## Timeline

- 2026-11-09: disclosed

## References

- [https://github.com/eclipse-langium/langium/security/advisories/GHSA-7c4f-7qwx-hmcv](https://github.com/eclipse-langium/langium/security/advisories/GHSA-7c4f-7qwx-hmcv)
- [https://gitlab.eclipse.org/security/cve-assignment/-/work_items/512](https://gitlab.eclipse.org/security/cve-assignment/-/work_items/512)

## Related threats

- [Eclipse Langium algorithmic complexity DoS in IndentationAwareTokenBuilder](https://junglewise.ai/threats/cve-2026-124683-eclipse-langium-versions-3-2-0-through-4-4-0-contain-an)