TOON: Prototype pollution when decoding untrusted TOON input
Published Sep 2, 2026 · Updated Nov 3, 2026
Original summary
Normalized public record · Updated Nov 3, 2026
TOON: Prototype pollution when decoding untrusted TOON input
Publisher and source text is retained separately from QFinch interpretation.
QFinch assessment
Decoding attacker-controlled TOON containing a proto, constructor, or prototype key wrote through the object's prototype chain instead of creating an own property, polluting Object.prototype for the whole runtime. The expandPaths: 'safe' path (dotted keys such as a.proto.x) was the strongest vector; plain nested objects, tabular rows, and quoted keys were all affected. The encoder had a matching defect: it silently dropped own proto properties and could fire an inherited setter while normalizing.
Potential impact
Any service that decodes untrusted TOON is affected. Prototype pollution can escalate to denial of service or, with a suitable downstream gadget, remote code execution.
Evidence: public source recordsAffected products
| Affected package, product or range | Fix status |
|---|---|
| Consult the referenced vendor advisory for affected versions. | Consult source advisory |
Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.
Remediation
Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.
- Confirm the affected product and reachable code path exist in your environment.
- Apply the vendor-supported patch or mitigation from the primary advisory.
- Rescan the exact deployed revision and retain verification evidence.
Evidence coverage
- SSVC priority
- MEDIUM
- Confidence
- Not available
- Aliases
- None reported
Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.
Sources and record history
Record history
Published Sep 2, 2026 · Last refreshed Nov 3, 2026