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Medium, CVSS 5.9amended

Serialize JavaScript has CPU Exhaustion Denial of Service via crafted array-like objects

CVE-2026-34043GHSA-qj8w-gfj5-8c6v

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (serialize-javascript 7.0.5), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS
  • CVE-2026-34043: 0.49% estimated exploitation activity in the next 30 days; percentile 42.24 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Impact What kind of vulnerability is it? It is a Denial of Service (DoS) vulnerability caused by CPU exhaustion. When serializing a specially crafted "array-like" object (an object that inherits from Array.prototype but has a very large length property), the process enters an intensive loop that consumes 100% CPU and hangs indefinitely. Who is impacted? Applications that use serialize-javascript to serialize untrusted or user-controlled objects are at risk. While direct exploitation is difficult, it becomes a high-priority threat if the application is also vulnerable to Prototype Pollution or handles untrusted data via YAML Deserialization, as these could be used to inject the malicious object. Patches Has the problem been patched? Yes, the issue has been patched by replacing instanceof Array checks with Array.isArray() and using Object.keys() for sparse array detection. What versions should users upgrade to? Users should upgrade to v7.0.5 or later. Workarounds Is there a way for…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-qj8w-gfj5-8c6v

  2. Revision 1 · created ·

    Published from osv record GHSA-qj8w-gfj5-8c6v

Agent brief

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# Patch Next advisory brief: CVE-2026-34043

Advisory: Serialize JavaScript has CPU Exhaustion Denial of Service via crafted array-like objects
IDs: CVE-2026-34043, GHSA-qj8w-gfj5-8c6v
Record: https://patchnext.com/advisories/cve-2026-34043 (revision 2, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: serialize-javascript 7.0.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm serialize-javascript: affected >= 5.0.0, < 7.0.5; fixed in 7.0.5

## 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-qj8w-gfj5-8c6v (OSV record GHSA-qj8w-gfj5-8c6v lists affected ranges: npm serialize-javascript >=5.0.0 <7.0.5 (fixed))
- Verified: https://github.com/advisories/GHSA-qj8w-gfj5-8c6v (GitHub-reviewed advisory GHSA-qj8w-gfj5-8c6v lists affected ranges: npm serialize-javascript >=5.0.0 <7.0.5)

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