CVE-2026-113603

MEDIUM 6.5

x402 @x402/extensions 2.3.1 through 2.28.0 SIWX Payment Bypass via PaymentPayload.resource

CVSS Score

6.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-639
Vendor	x402-foundation
Product	@x402/extensions
Published	Oct 20, 2026

Stay Ahead of the Next One

Get instant alerts for x402-foundation @x402/extensions

Be the first to know when new medium vulnerabilities affecting x402-foundation @x402/extensions are published — delivered to Slack, Telegram or Discord.

Get Free Alerts → Free · No credit card · 60 sec setup

CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Affected Versions

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

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/x402-foundation/x402/issues/3838 github.com: https://github.com/x402-foundation/x402/pull/3840 github.com: https://github.com/x402-foundation/x402/blob/npm-@x402/[email protected]/typescript/packages/extensions/src/sign-in-with-x/hooks.ts github.com: https://github.com/x402-foundation/x402/blob/[email protected]/python/x402/extensions/sign_in_with_x/hooks.py github.com: https://github.com/x402-foundation/x402/blob/go/v2.28.0/go/extensions/signinwithx/server.go vulncheck.com: https://www.vulncheck.com/advisories/x402-x402-extensions-2.3.1-through-2.28.0-siwx-payment-bypass-via-paymentpayload-resource

Credits

CBF, Lza