Disclosed weakness · no CVE recorded

x402: Agent-payment verification and signing weaknesses

x402 maintainers · x402 TypeScript payment facilitators and automatic clients

First documented disclosure · Review checkpoint

Summary

V12 disclosed three detailed critical findings within a larger 25-finding review of agent-payment software.

Severity and exploitation evidence

No CVSS score recorded in this review.

Exploitation not established: The reviewed sources establish a disclosed weakness or researcher demonstration, not malicious exploitation in the wild.

Technical severity is not a measure of observed attacks or of risk to your deployment. Attempts, demonstrations, and successful compromise retain the qualifications in the source.

How the weakness works

Missing transaction-type checks, unbound login domains and absent spending budgets crossed payment trust boundaries.

Conditions required

An affected facilitator or automatic signing client interacting with attacker-controlled payment data.

Potential impact

Potential unpaid resource access, relayed wallet login or excessive token authorization.

Affected versions and configurations

Described TypeScript v1/v2 exact-scheme and automatic-client paths; no complete package-version range supplied.

Fix and mitigation status

V12 says the three critical findings were fixed by August 20; exact release mapping is not provided.

Practical next steps

Verify current upstream fixes; bind signatures to the intended origin and enforce spending limits before signing.

Operating lesson

Payment schemas and cryptographic signatures do not establish user intent or an acceptable budget.

Evidence and limits

Local research tests, not documented victim losses. The Solana test did not submit a live transaction. The publication does not establish remediation of all 25 findings.

Related incident and research records

Related records can include laboratory demonstrations; a relationship does not itself establish exploitation.

Sources