CVE-2026-113603
x402 @x402/extensions 2.3.1 through 2.28.0 SIWX Payment Bypass via PaymentPayload.resource
- State
- Published
- Severity
- 6.9 Medium
- Published
- Oct 20, 2026
- Updated
- Oct 21, 2026
- Reserved
- Oct 20, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.9 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 6.5 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N | VulnCheck |
Weaknesses
- CWE-639 Authorization Bypass Through User-Controlled Key
Affected Products
| Product | Versions |
|---|---|
@x402/extensionsx402-foundation |
|
x402x402-foundation |
|
github.com/x402-foundation/x402/go/v2x402-foundation |
|
References
- https://github.com/x402-foundation/x402/issues/3838issue-tracking
- https://github.com/x402-foundation/x402/pull/3840patchissue-tracking
- https://github.com/x402-foundation/x402/blob/npm-@x402/extensions@v2.28.0/typescript/packages/extensions/src/sign-in-with-x/hooks.tstechnical-description
- https://github.com/x402-foundation/x402/blob/pypi-x402@v2.25.0/python/x402/extensions/sign_in_with_x/hooks.pytechnical-description
- https://github.com/x402-foundation/x402/blob/go/v2.28.0/go/extensions/signinwithx/server.gotechnical-description
- VulnCheck Advisory: x402 @x402/extensions 2.3.1 through 2.28.0 SIWX Payment Bypass via PaymentPayload.resourcethird-party-advisory
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