Vega vulnerable to Cross-site Scripting via RegExp.prototype[@@replace]

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N · score source

EPSS

• CVE-2025-27793: 0.52% estimated exploitation activity in the next 30 days; percentile 44.02 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Users running Vega/Vega-lite JSON definitions could run unexpected JavaScript code when drawing graphs, unless the library is used with the vega-interpreter. Workarounds - Use vega with expression interpreter - Upgrade to a newer Vega version (5.32.0) POC Summary Calling replace with a RegExp-like pattern calls RegExp.prototype[@@replace], which can then call an attacker-controlled exec function. POC Details Consider the function call replace('foo', {proto: /h/.constructor.prototype, global: false}). Since pattern has RegExp.prototype[@@replace], pattern.exec('foo') winds up being called. The resulting malicious call looks like this: Since functions cannot be returned from this, an attacker that wishes to escalate to XSS must abuse event.view to gain access to eval. Reproduction steps

Published by the source

27 Mar 2025, 18:00 UTC

Last modified by the source

27 Mar 2025, 18:08 UTC

Source last checked

26 Oct 2026, 12:36 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-963h-3v39-3pqf

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-963h-3v39-3pqf

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# Patch Next advisory brief: CVE-2025-27793

Advisory: Vega vulnerable to Cross-site Scripting via RegExp.prototype[@@replace]
IDs: CVE-2025-27793, GHSA-963h-3v39-3pqf
Record: https://patchnext.com/advisories/cve-2025-27793 (revision 3, source checked 26 Oct 2026, 12:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: vega 5.32.0; vega-functions 5.17.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm vega: affected < 5.32.0; fixed in 5.32.0
- npm vega-functions: affected < 5.17.0; fixed in 5.17.0

## Suggested inspection (read-only)
- `npm ls vega --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls vega-functions --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on vega, vega-functions.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-963h-3v39-3pqf (OSV record GHSA-963h-3v39-3pqf lists affected ranges: npm vega >=0 =0 <5.17.0 (fixed))
- Verified: https://github.com/advisories/GHSA-963h-3v39-3pqf (GitHub-reviewed advisory GHSA-963h-3v39-3pqf lists affected ranges: npm vega >=0 =0 <5.17.0)

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