CVE-2026-113603 PUBLISHED

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

Assigner: VulnCheck
Reserved: 20.10.2026 Published: 20.10.2026 Updated: 20.10.2026

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.

Metrics

CVSS 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
CVSS Score: 6.9

Product Status

Vendor x402-foundation
Product @x402/extensions
Versions Default: unaffected
  • affected from 2.3.1 to 2.28.0 (incl.)
Vendor x402-foundation
Product x402
Versions Default: unaffected
  • affected from 2.11.0 to 2.25.0 (incl.)
Vendor x402-foundation
Product github.com/x402-foundation/x402/go/v2
Versions Default: unaffected
  • affected from 2.16.0 to 2.28.0 (incl.)

Credits

  • CBF, Lza finder

References

Problem Types

  • Authorization Bypass Through User-Controlled Key CWE