Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') Affecting renovate package, versions <43.84.0-r1


Severity

Recommended
0.0
critical
0
10

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Threat Intelligence

EPSS
0.01% (3rd percentile)

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  • Snyk IDSNYK-CHAINGUARDLATEST-RENOVATE-15753990
  • published23 Mar 2026
  • disclosed20 Mar 2026

Introduced: 20 Mar 2026

NewCVE-2026-33228  (opens in a new tab)
CWE-1321  (opens in a new tab)

How to fix?

Upgrade Chainguard renovate to version 43.84.0-r1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream renovate package and not the renovate package as distributed by Chainguard. See How to fix? for Chainguard relevant fixed versions and status.

flatted is a circular JSON parser. Prior to version 3.4.2, the parse() function in flatted can use attacker-controlled string values from the parsed JSON as direct array index keys, without validating that they are numeric. Since the internal input buffer is a JavaScript Array, accessing it with the key "proto" returns Array.prototype via the inherited getter. This object is then treated as a legitimate parsed value and assigned as a property of the output object, effectively leaking a live reference to Array.prototype to the consumer. Any code that subsequently writes to that property will pollute the global prototype. This issue has been patched in version 3.4.2.

CVSS Base Scores

version 3.1