Serialize JavaScript is Vulnerable to RCE via RegExp.flags and Date.prototype.toISOString()

Exploitation

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

CVSS

8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact The serialize-javascript npm package (versions <= 7.0.2) contains a code injection vulnerability. It is an incomplete fix for CVE-2020-7660. While RegExp.source is sanitized, RegExp.flags is interpolated directly into the generated output without escaping. A similar issue exists in Date.prototype.toISOString(). If an attacker can control the input object passed to serialize(), they can inject malicious JavaScript via the flags property of a RegExp object. When the serialized string is later evaluated (via eval, new Function, or <script tags), the injected code executes. Patches The fix has been published in version 7.0.3. https://github.com/yahoo/serialize-javascript/releases/tag/v7.0.3

Published by the source

28 Feb 2026, 02:50 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-5c6j-r48x-rmvq

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-5c6j-r48x-rmvq

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# Patch Next advisory brief: GHSA-5c6j-r48x-rmvq

Advisory: Serialize JavaScript is Vulnerable to RCE via RegExp.flags and Date.prototype.toISOString()
IDs: GHSA-5c6j-r48x-rmvq
Record: https://patchnext.com/advisories/ghsa-5c6j-r48x-rmvq (revision 2, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: serialize-javascript 7.0.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm serialize-javascript: affected <= 7.0.2; fixed in 7.0.3

## Suggested inspection (read-only)
- `npm ls serialize-javascript --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 serialize-javascript.
- 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-5c6j-r48x-rmvq (OSV record GHSA-5c6j-r48x-rmvq lists affected ranges: npm serialize-javascript >=0 <7.0.3 (fixed))
- Verified: https://github.com/advisories/GHSA-5c6j-r48x-rmvq (GitHub-reviewed advisory GHSA-5c6j-r48x-rmvq lists affected ranges: npm serialize-javascript >=0 <=7.0.2)

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