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Vulnerability · Published Oct 20, 2026 · Assigned by VulnCheck

CVE-2026-113603x402 @x402/extensions 2.3.1 through 2.28.0 SIWX Payment Bypass via PaymentPayload.resource

Medium 6.5

In plain English

A medium-severity authorization bypass via user-controlled key in github.com/x402-foundation/x402/go/v2 from x402-foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 29% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.4%top 70.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

The x402 SIWX server extension in @x402/extensions 2.3.1 through 2.28.0, x402 PyPI 2.11.0 through 2.25.0, and Go module 2.16.0 through 2.28.0 contains an authorization bypass vulnerability that allows paying clients to unlock unpaid routes by supplying a mismatched PaymentPayload.resource URL. Attackers can pay for the cheapest SIWX-protected route while setting resource.url to an expensive route, then repeatedly access it using only a SIGN-IN-WITH-X header without further payment.

Affected products (as reported)

VendorProductVersions
x402-foundation @x402/extensions 2.3.1 – through 2.28.0
x402-foundation x402 2.11.0 – through 2.25.0
x402-foundation github.com/x402-foundation/x402/go/v2 2.16.0 – through 2.28.0

Weakness: CWE-639 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References