CVE-2026-82404Network attack vectorHinoki check available

Runtime prototype pollution via unsafe decoded-key writes

Published Sep 2, 2026 · Updated Sep 2, 2026

Prototype pollution in TOON before 2.3.1 allows remote attackers to corrupt the runtime object prototype via crafted TOON input. Decoder paths including insertPathSafe assigned attacker-controlled proto, constructor, and prototype keys through inherited accessors instead of defining own data properties. A service must decode untrusted TOON; pollution can crash the process or enable remote code execution when a suitable downstream gadget exists.

CVSS severity8.3
High
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Prototype pollution in TOON before 2.3.1 allows remote attackers to corrupt the runtime object prototype via crafted TOON input. Decoder paths including insertPathSafe assigned attacker-controlled proto, constructor, and prototype keys through inherited accessors instead of defining own data properties. A service must decode untrusted TOON; pollution can crash the process or enable remote code execution when a suitable downstream gadget exists.

The record

CVE
CVE-2026-82404
Published
Sep 2, 2026
Updated
Sep 2, 2026
Vendor
TOON
Product
TOON
Classifications
CWE-1321, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 2, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

TOON · TOONversion=< 2.3.1

Published CVSS scores

8.3GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo