CVE-2025-59840 — vega
HIGHCVE-2025-59840 is a high-severity (CVSS 8.1) Cross-site Scripting (XSS) vulnerability in vega. A fix is available for vega — see the affected versions and patch details below.
Vega Cross-Site Scripting (XSS) via expressions abusing toString calls in environments using the VEGA_DEBUG global variable
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-59840.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2025-59840 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,333 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
veganpmvega-expressionnpmvega-interpreternpmDescription
Vega is a visualization grammar, a declarative format for creating, saving, and sharing interactive visualization designs. In Vega prior to version 6.2.0, applications meeting 2 conditions are at risk of arbitrary JavaScript code execution, even if "safe mode" expressionInterpreter is used. They are vulnerable if they use vega in an application that attaches vega library and a vega.View instance similar to the Vega Editor to the global window and if they allow user-defined Vega JSON definitions (vs JSON that was is only provided through source code). Patches are available in the following Vega applications. If using the latest Vega line (6.x), upgrade to vega 6.2.0 / vega-expression 6.1.0 / vega-interpreter 2.2.1 (if using AST evaluator mode). If using Vega in a non-ESM environment, upgrade to vega-expression 5.2.1 / 1.2.1 (if using AST evaluator mode). Some workarounds are available. Do not attach vega View instances to global variables, and do not attach vega to the global window. These practices of attaching the vega library and View instances may be convenient for debugging, but should not be used in production or in any situation where vega/vega-lite definitions could be provided by untrusted parties.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | vega | all versions | 6.2.0npm install vega@6.2.0 |
| 📦npm | vega-expression | ≥ 6.0.0&&< 6.1.0 | 6.1.0npm install vega-expression@6.1.0 |
| 📦npm | vega-interpreter | ≥ 2.0.0&&< 2.2.1 | 2.2.1npm install vega-interpreter@2.2.1 |
| 📦npm | vega-interpreter | all versions | 1.2.1npm install vega-interpreter@1.2.1 |
| 📦npm | vega-expression | all versions | 5.2.1npm install vega-expression@5.2.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vega, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vega to 6.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-59840 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-59840 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-59840. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-59840 in your dependencies?
O3 Security finds CVE-2025-59840 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.