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.
Published: 2026-10-20
Score: 6.9 Medium
EPSS: < 1% Very Low
KEV: No
AI Analysis

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Remediation

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Tracking

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Advisories

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History

Wed, 21 Oct 2026 17:15:00 +0000

Type Values Removed Values Added
First Time appeared X402-foundation
X402-foundation x402
Vendors & Products X402-foundation
X402-foundation x402
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Tue, 20 Oct 2026 15:45:00 +0000

Type Values Removed Values Added
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.
Title x402 @x402/extensions 2.3.1 through 2.28.0 SIWX Payment Bypass via PaymentPayload.resource
Weaknesses CWE-639
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}

cvssV4_0

{'score': 6.9, 'vector': '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'}

Subscriptions

X402-foundation X402
cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-21T15:54:28.895Z

Reserved: 2026-10-20T11:48:49.343Z

Link: CVE-2026-113603

cve-icon Vulnrichment

Updated: 2026-10-21T14:40:26.987Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-20T16:17:10.087

Modified: 2026-10-21T16:17:23.530

Link: CVE-2026-113603

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-21T16:44:31Z

Weaknesses