{"id":"CVE-2026-113603","title":"x402 @x402/extensions 2.3.1 through 2.28.0 SIWX Payment Bypass via PaymentPayload.resource","summary":"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 rout…","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N","cvssSource":"cna","cwe":["CWE-639"],"vendor":"x402-foundation","product":"@x402/extensions","affected":["@x402/extensions >= 2.3.1 <= 2.28.0","x402 >= 2.11.0 <= 2.25.0","github.com/x402-foundation/x402/go/v2 >= 2.16.0 <= 2.28.0"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-21T14:40:26.284069Z"},"published":"2026-10-20","updated":"2026-10-21","sourceUpdated":"2026-10-21T15:54:28.895Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-113603","references":[{"url":"https://github.com/x402-foundation/x402/issues/3838"},{"url":"https://github.com/x402-foundation/x402/pull/3840"},{"url":"https://github.com/x402-foundation/x402/blob/npm-@x402/extensions@v2.28.0/typescript/packages/extensions/src/sign-in-with-x/hooks.ts"},{"url":"https://github.com/x402-foundation/x402/blob/pypi-x402@v2.25.0/python/x402/extensions/sign_in_with_x/hooks.py"},{"url":"https://github.com/x402-foundation/x402/blob/go/v2.28.0/go/extensions/signinwithx/server.go"},{"url":"https://www.vulncheck.com/advisories/x402-x402-extensions-2.3.1-through-2.28.0-siwx-payment-bypass-via-paymentpayload-resource","label":"VulnCheck Advisory: x402 @x402/extensions 2.3.1 through 2.28.0 SIWX Payment Bypass via PaymentPayload.resource"}],"tags":["cve.org"],"epss":0.00291,"epssPercentile":0.20495,"ingestedAt":"2026-10-20T16:10:53.303Z","slug":"CVE-2026-113603","body":"## Overview\n\nThe 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.\n\n## Affected\n\n- `@x402/extensions >= 2.3.1 <= 2.28.0`\n- `x402 >= 2.11.0 <= 2.25.0`\n- `github.com/x402-foundation/x402/go/v2 >= 2.16.0 <= 2.28.0`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}