CVE-2026-120350: Vaadin stored XSS in rich text editor

Summary

The Vaadin Rich Text Editor, in versions 25.0 through 25.3 before the listed fixes, lets an attacker who can edit shared content store a video embed that runs script in the browser of any user who opens the page. The attack is carried out remotely over the network, but it needs a low-privilege login and a user to open the affected content.

Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.

Read the original description

The Vaadin Rich Text Editor exports a video embed without escaping its value, and then parses the resulting HTML into live DOM. A value crafted to break out of the href attribute therefore runs script in the viewer's browser. An attacker who can edit shared content pastes a video embed carrying the payload, the delta is stored, and the script runs when any user opens the page, including in read only mode.

Only content persisted through asDelta() is affected. The default HTML value, set and read through setValue and getValue, is sanitized on the server with a safelist that has no iframe, so the embed does not survive that path. Vaadin 24 and older are not affected: they build the HTML value from the editor's own innerHTML, which the browser escapes.

Users of affected versions should apply the following mitigation or upgrade. Releases that have fixed this issue include:

Product version Vaadin 25.0.0 - 25.0.13 Vaadin 25.1.0 - 25.1.13 Vaadin 25.2.0 - 25.2.12 Vaadin 25.3.0 - 25.3.4

Mitigation No fixed release on this line, upgrade to 25.2.13 or newer No fixed release on this line, upgrade to 25.2.13 or newer Upgrade to 25.2.13 Upgrade to 25.3.5

cve.now Index

18Pcve.now Index 18 of 100 · methodology v3 · provisional

Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
Exposure3/25Reachable over the network · Unknown: No advisory context yet
Reach10/20Affects Maven, npm packages
Severity5.1/10CVSS 5.1
No patch0/5No signal

What would change the score

Would score about 73 if added to CISA KEV
Would score about 68 if CISA's SSVC rates exploitation active
Would score about 37 if advisories confirm default setups are exposed

How the score works · Rankings

What to do

Upgrade to a fixed version: com.vaadin:vaadin 25.2.13, 25.3.5 · com.vaadin:vaadin-core 25.2.13, 25.3.5 · com.vaadin:vaadin-rich-text-editor-flow 25.2.13, 25.3.5 · @vaadin/rich-text-editor 25.3.5, 25.2.17.

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

Check whether my systems are affected by CVE-2026-120350 (Stored Cross-Site Scripting in the Vaadin Rich Text Editor via an Unescaped Video Embed), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-120350 (entry last updated 2026-11-10):
Affected:
- Maven package com.vaadin:vaadin: from 25.0.0, through 25.0.13; from 25.1.0, through 25.1.13; from 25.2.0, fixed in 25.2.13; from 25.3.0, fixed in 25.3.5
- Maven package com.vaadin:vaadin-core: from 25.0.0, through 25.0.13; from 25.1.0, through 25.1.13; from 25.2.0, fixed in 25.2.13; from 25.3.0, fixed in 25.3.5
- Maven package com.vaadin:vaadin-rich-text-editor-flow: from 25.0.0, through 25.0.13; from 25.1.0, through 25.1.13; from 25.2.0, fixed in 25.2.13; from 25.3.0, fixed in 25.3.5
- npm package @vaadin/rich-text-editor: from 25.0.0, through 25.0.13; from 25.1.0, through 25.1.14; from 25.2.0, fixed in 25.2.17; from 25.3.0, fixed in 25.3.5
Fixed versions: 25.2.13, 25.3.5, 25.2.17.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-120350 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-120350 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (Maven, npm): find every lockfile in each project and run check_stack from the cve.now MCP server on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://vaadin.com/security/cve-2026-120350
- https://github.com/vaadin/web-components/pull/13272
- https://github.com/advisories/GHSA-v3m3-f69x-jf25
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-120350
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-120350.

Timeline

Nov 10, 2026, 11:50 AM UTCCVE published
Nov 10, 2026, 11:58 AM UTCFirst seen by cve.now

Affected versions

com.vaadin:vaadinMaven
From 25.0.0 · through 25.0.13; From 25.1.0 · through 25.1.13; From 25.2.0 · fixed in 25.2.13; From 25.3.0 · fixed in 25.3.5
com.vaadin:vaadin-coreMaven
From 25.0.0 · through 25.0.13; From 25.1.0 · through 25.1.13; From 25.2.0 · fixed in 25.2.13; From 25.3.0 · fixed in 25.3.5
com.vaadin:vaadin-rich-text-editor-flowMaven
From 25.0.0 · through 25.0.13; From 25.1.0 · through 25.1.13; From 25.2.0 · fixed in 25.2.13; From 25.3.0 · fixed in 25.3.5
@vaadin/rich-text-editornpm
From 25.0.0 · through 25.0.13; From 25.1.0 · through 25.1.14; From 25.2.0 · fixed in 25.2.17; From 25.3.0 · fixed in 25.3.5

Evidence 5

Vendor advisory · 1

Establishes: Affected and fixed versions.

Link
vaadin.com · security/cve-2026-120350

CVE record · 2

Establishes: The identifier and description.

Record
CVE List · CVE-2026-120350
Record
NVD · CVE-2026-120350

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about CVE-2026-120350

Is CVE-2026-120350 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: cve.now feed data

Which versions are affected by CVE-2026-120350?

com.vaadin:vaadin (Maven): from 25.0.0 through 25.0.13; from 25.1.0 through 25.1.13; from 25.2.0 before 25.2.13; from 25.3.0 before 25.3.5. com.vaadin:vaadin-core (Maven): from 25.0.0 through 25.0.13; from 25.1.0 through 25.1.13; from 25.2.0 before 25.2.13; from 25.3.0 before 25.3.5. com.vaadin:vaadin-rich-text-editor-flow (Maven): from 25.0.0 through 25.0.13; from 25.1.0 through 25.1.13; from 25.2.0 before 25.2.13; from 25.3.0 before 25.3.5. @vaadin/rich-text-editor (npm): from 25.0.0 through 25.0.13; from 25.1.0 through 25.1.14; from 25.2.0 before 25.2.17; from 25.3.0 before 25.3.5.Source: cve.now feed data

How do I fix CVE-2026-120350?

Upgrade to a fixed version: com.vaadin:vaadin 25.2.13, 25.3.5 · com.vaadin:vaadin-core 25.2.13, 25.3.5 · com.vaadin:vaadin-rich-text-editor-flow 25.2.13, 25.3.5 · @vaadin/rich-text-editor 25.3.5, 25.2.17.Source: cve.now feed data

Stored Cross-Site Scripting in the Vaadin Rich Text Editor via an Unescaped Video Embed