CVE-2025-27793: Vega Visualization Grammar XSS Vulnerability

CVE-2025-27793 Overview

CVE-2025-27793 affects Vega, a visualization grammar library used to create declarative interactive visualizations. Versions of Vega prior to 5.32.0 and corresponding vega-functions versions prior to 5.17.0 allow unexpected JavaScript execution when rendering Vega or Vega-Lite JSON definitions. The flaw is classified as Cross-Site Scripting under [CWE-79]. Users of the vega-interpreter are not affected. The maintainers released Vega 5.32.0 and vega-functions 5.17.0 to remediate the issue.

Critical Impact
Attacker-controlled Vega or Vega-Lite JSON specifications can trigger unintended JavaScript execution in the rendering context, enabling client-side script injection against applications that render untrusted visualizations.

Affected Products

Vega versions prior to 5.32.0
vega-functions versions prior to 5.17.0
Applications rendering untrusted Vega/Vega-Lite JSON without the vega-interpreter

Discovery Timeline

2025-03-27 - CVE-2025-27793 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-27793

Vulnerability Analysis

Vega parses declarative JSON specifications and evaluates embedded expressions to drive interactive visualizations. Prior to version 5.32.0, the default expression evaluation path allowed constructs that could reach JavaScript execution primitives outside the intended expression sandbox. An attacker who controls the visualization specification can craft expression fields that break out of Vega's expected evaluation surface.

The vulnerability is reachable in browser contexts where Vega renders user-supplied or third-party JSON. It carries a network attack vector and requires user interaction such as loading a page containing the malicious specification. The scope extends beyond the vulnerable component, affecting the confidentiality and integrity of the rendering page context.

Root Cause

The root cause lies in vega-functions expression handlers that did not sufficiently validate input types before dispatching to underlying JavaScript operations. The patch commit adds an isRegExp type check imported from vega-util in packages/vega-functions/src/functions/sequence.js, tightening argument validation to prevent unexpected code paths.

Attack Vector

Exploitation requires an application to render an attacker-supplied Vega or Vega-Lite specification using the default expression evaluator. This scenario is common in dashboards, notebooks, and analytics platforms that accept user-authored visualizations. Once rendered, embedded JavaScript executes in the origin of the hosting page, exposing session tokens, cookies, and DOM contents.

javascript

// Patch excerpt: packages/vega-functions/src/functions/sequence.js
-import { ascending, error, isArray, isFunction, isString } from 'vega-util';
+import { ascending, error, isArray, isFunction, isRegExp, isString } from 'vega-util';
 
 function array(seq) {
   return isArray(seq) || ArrayBuffer.isView(seq) ? seq : null;

Source: GitHub Commit 694560c

Detection Methods for CVE-2025-27793

Indicators of Compromise

Vega or Vega-Lite JSON specifications containing suspicious expr, signal, or on fields referencing constructor chains or global object access
Unexpected outbound requests from browser sessions immediately after rendering third-party visualizations
Client-side script errors or console warnings originating from vega-functions modules

Detection Strategies

Inventory application dependencies to identify Vega versions below 5.32.0 and vega-functions below 5.17.0 using tools such as npm ls vega vega-functions
Inspect build manifests and Software Bill of Materials (SBOM) records for vulnerable package versions
Review server logs for user-uploaded Vega specifications and flag payloads containing unusual expression syntax

Monitoring Recommendations

Monitor Content Security Policy (CSP) violation reports for inline script or eval events on pages that render Vega content
Alert on anomalous JavaScript execution patterns in browser telemetry from analytics or dashboard applications
Track dependency scanner findings for the GHSA-963h-3v39-3pqf advisory identifier

How to Mitigate CVE-2025-27793

Immediate Actions Required

Upgrade Vega to version 5.32.0 or later and vega-functions to 5.17.0 or later across all applications
Audit any code path that ingests user-controlled Vega or Vega-Lite JSON and restrict its origins
Deploy a strict Content Security Policy that blocks inline script execution on pages rendering visualizations

Patch Information

The fix is available in Vega 5.32.0 and vega-functions 5.17.0. Full details are published in the GitHub Security Advisory GHSA-963h-3v39-3pqf and the Vega v5.32.0 Release Notes. The upstream fix is committed in commit 694560c.

Workarounds

Switch to the vega-interpreter expression evaluator, which is not affected by this vulnerability
Sanitize or reject Vega specifications from untrusted sources before rendering
Isolate visualization rendering inside a sandboxed iframe with restricted origin privileges

bash

# Upgrade Vega and use the expression interpreter
npm install vega@^5.32.0 vega-functions@^5.17.0 vega-interpreter

# Reference: https://vega.github.io/vega/usage/interpreter
# Initialize Vega view with interpreter option
# new vega.View(runtime, { expr: vegaInterpreter.expressionInterpreter })