flat through 6.0.1 Denial of Service via unflatten() Numeric Array Index Keys

Summary

flat through 6.0.1 contains an uncontrolled resource allocation vulnerability in unflatten() that allows attackers to create huge sparse arrays via unbounded numeric keys. Attackers can supply flattened keys such as a.4294967294, causing iteration with forEach, spread or JSON.stringify to block the Node.js event loop.

Remediation

1. Inventory every hughsk flat deployment, including staging.
2. No fixed version appears in the public sources yet. Check the references below and the vendor directly.

References

• Advisoryhttps://www.vulncheck.com/advisories/flat-through-6.0.1-denial-of-service-via-unflatten-numeric-array-index-keys
• Referencehttps://github.com/hughsk/flat/issues/195
• Referencehttps://github.com/hughsk/flat
• Referencehttps://github.com/hughsk/flat/blob/1d68e1d06c0210cff31e5c61ac177f3e2d3fa564/index.js#L65-L75
• Referencehttps://github.com/hughsk/flat/blob/1d68e1d06c0210cff31e5c61ac177f3e2d3fa564/index.js#L137-L142