CVE-2026-119051
flat through 6.0.1 Denial of Service via unflatten() Numeric Array Index Keys
CVSS Score
5.9
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-770 |
| Vendor | hughsk |
| Product | flat |
| Published | Oct 29, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
hughsk / flat
0 ≤ 6.0.1
References
github.com: https://github.com/hughsk/flat/issues/195 github.com: https://github.com/hughsk/flat github.com: https://github.com/hughsk/flat/blob/1d68e1d06c0210cff31e5c61ac177f3e2d3fa564/index.js#L65-L75 github.com: https://github.com/hughsk/flat/blob/1d68e1d06c0210cff31e5c61ac177f3e2d3fa564/index.js#L137-L142 vulncheck.com: https://www.vulncheck.com/advisories/flat-through-6.0.1-denial-of-service-via-unflatten-numeric-array-index-keys
Credits
Yu Bao, PayPal Cyber Security Team