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

Quick assessment

Affected
x402-foundation @x402/extensions
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 2.3.1 至 2.28.0 版本、x402 PyPI 2.11.0 至 2.25.0 版本，以及 Go 模块 2.16.0 至 2.28.0 版本中，x402 SIWX 服务器扩展存在一个授权绕过漏洞。该漏洞允许已付费的客户端通过提供与支付不匹配的 URL，来解锁未付费的接口。攻击者可以仅支付最便宜的受 SIWX 保护的接口费用，同时将 设置为一个昂贵接口的地址，随后仅凭 请求头反复访问该昂贵接口，而无需再次支付。

CVSS 6.5 · Medium

Affected Version Matrix 3

VendorProduct Version RangeStatus
x402-foundation @x402/extensions 2.3.1≤ 2.28.0 affected
x402-foundation github.com/x402-foundation/x402/go/v2 2.16.0≤ 2.28.0 affected
x402-foundation x402 2.11.0≤ 2.25.0 affected
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I. Basic Information for CVE-2026-113603

Vulnerability Information
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Vulnerability Title
x402 @x402/extensions 2.3.1 through 2.28.0 SIWX Payment Bypass via PaymentPayload.resource
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
x402-foundation @x402/extensions 2.3.1 ~ 2.28.0 -
x402-foundation x402 2.11.0 ~ 2.25.0 -
x402-foundation github.com/x402-foundation/x402/go/v2 2.16.0 ~ 2.28.0 -

II. Public POCs for CVE-2026-113603

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III. Intelligence Information for CVE-2026-113603

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Other References for CVE-2026-113603 (6)

IV. Related Vulnerabilities

Same weakness: CWE-639

V. Comments for CVE-2026-113603

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