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Medium

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

Type: advisorySources: OSV

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.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-113603
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 02:24 UTC · Revision 1

Source evidence

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

core-osv · Original source

Published 20 Oct 2026, 15:40 UTC

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.

osv:CVE-2026-113603
Complete source record
{
  "id": "154edfd02147c6f23d5972f227c30d80cb6bbb36ddcf494a740f85d5ab43577a",
  "url": "https://osv.dev/vulnerability/CVE-2026-113603",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "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 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.",
    "evidence": "osv:CVE-2026-113603",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-113603",
      "aliases": [
        "CVE-2026-113603"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/x402-foundation/x402",
              "type": "GIT",
              "events": [
                {
                  "introduced": "dd49a436183aaa72f3a8e2d8b82d8cc226fb6e5e"
                },
                {
                  "last_affected": "6b6ee91fee027b540faabcb25774e73851006c3b"
                },
                {
                  "introduced": "c03f1a8cb3ff36463b91531dbd0c701ddcdf3ffa"
                },
                {
                  "last_affected": "6b6ee91fee027b540faabcb25774e73851006c3b"
                },
                {
                  "introduced": "67b1ba0a7abbd7907a28fa624670872532e0eae9"
                },
                {
                  "last_affected": "6b6ee91fee027b540faabcb25774e73851006c3b"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "2.3.1"
                      },
                      {
                        "last_affected": "2.28.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "2.11.0"
                      },
                      {
                        "last_affected": "2.25.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "2.16.0"
                      },
                      {
                        "last_affected": "2.28.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  }
                ]
              }
            }
          ],
          "versions": [
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            "npm-@x402/near@v2.28.0",
            "npm-@x402/mcp@v2.28.0",
            "npm-@x402/keeta@v2.28.0",
            "npm-@x402/hono@v2.28.0",
            "npm-@x402/hedera@v2.28.0",
            "npm-@x402/fetch@v2.28.0",
            "npm-@x402/fastify@v2.28.0",
            "npm-@x402/extensions@v2.28.0",
            "npm-@x402/express@v2.28.0",
            "npm-@x402/evm@v2.28.0",
            "npm-@x402/core@v2.28.0",
            "npm-@x402/concordium@v2.28.0",
            "npm-@x402/casper@v2.28.0",
            "npm-@x402/cardano@v2.28.0",
            "npm-@x402/axios@v2.28.0",
            "npm-@x402/avm@v2.28.0",
            "npm-@x402/aptos@v2.28.0",
            "go/v2.28.0",
            "go-x402@v2.28.0",
            "pypi-x402@v2.24.0",
            "npm-@x402/xrpl@v2.27.0",
            "npm-@x402/tvm@v2.27.0",
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            "npm-@x402/avm@v2.27.0",
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            "go/v2.27.0",
            "go-x402@v2.27.0",
            "pypi-x402@v2.23.0",
            "npm-@x402/xrpl@v2.26.0",
            "npm-@x402/tvm@v2.26.0",
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            "npm-@x402/stellar@v2.26.0",
            "npm-@x402/paywall@v2.26.0",
            "npm-@x402/next@v2.26.0",
            "npm-@x402/near@v2.26.0",
            "npm-@x402/mcp@v2.26.0",
            "npm-@x402/keeta@v2.26.0",
            "npm-@x402/hono@v2.26.0",
            "npm-@x402/hedera@v2.26.0",
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            "npm-@x402/aptos@v2.26.0",
            "go/v2.26.0",
            "go-x402@v2.26.0",
            "pypi-x402@v2.22.0",
            "npm-@x402/xrpl@v2.25.0",
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            "npm-@x402/stellar@v2.25.0",
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            "npm-@x402/hono@v2.25.0",
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            "npm-@x402/fetch@v2.25.0",
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            "npm-@x402/extensions@v2.25.0",
            "npm-@x402/express@v2.25.0",
            "npm-@x402/evm@v2.25.0",
            "npm-@x402/core@v2.25.0",
            "npm-@x402/concordium@v2.25.0",
            "npm-@x402/axios@v2.25.0",
            "npm-@x402/avm@v2.25.0",
            "npm-@x402/aptos@v2.25.0",
            "go/v2.25.0",
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            "npm-@x402/svm@v2.24.0",
            "npm-@x402/stellar@v2.24.0",
            "npm-@x402/paywall@v2.24.0",
            "npm-@x402/next@v2.24.0",
            "npm-@x402/near@v2.24.0",
            "npm-@x402/mcp@v2.24.0",
            "npm-@x402/keeta@v2.24.0",
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            "npm-@x402/hedera@v2.24.0",
            "npm-@x402/fetch@v2.24.0",
            "npm-@x402/fastify@v2.24.0",
            "npm-@x402/extensions@v2.24.0",
            "npm-@x402/express@v2.24.0",
            "npm-@x402/evm@v2.24.0",
            "npm-@x402/core@v2.24.0",
            "npm-@x402/concordium@v2.24.0",
            "npm-@x402/axios@v2.24.0",
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            "npm-@x402/axios@v2.22.0",
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            "npm-@x402/aptos@v2.22.0",
            "go/v2.22.0",
            "go-x402@v2.22.0",
            "pypi-x402@v2.18.0",
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            "npm-@x402/aptos@v2.20.0",
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            "npm-@x402/next@v2.19.0",
            "npm-@x402/near@v2.19.0",
            "npm-@x402/mcp@v2.19.0",
            "npm-@x402/keeta@v2.19.0",
            "npm-@x402/hono@v2.19.0",
            "npm-@x402/hedera@v2.19.0",
            "npm-@x402/fetch@v2.19.0",
            "npm-@x402/fastify@v2.19.0",
            "npm-@x402/extensions@v2.19.0",
            "npm-@x402/express@v2.19.0",
            "npm-@x402/evm@v2.19.0",
            "npm-@x402/core@v2.19.0",
            "npm-@x402/concordium@v2.19.0",
            "npm-@x402/axios@v2.19.0",
            "npm-@x402/avm@v2.19.0",
            "npm-@x402/aptos@v2.19.0",
            "go/v2.19.0",
            "go-x402@v2.19.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-113603.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:32.404576449Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/113xxx/CVE-2026-113603.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-113603",
        "https://www.vulncheck.com/advisories/x402-x402-extensions-2.3.1-through-2.28.0-siwx-payment-bypass-via-paymentpayload-resource",
        "https://github.com/x402-foundation/x402/issues/3838",
        "https://github.com/x402-foundation/x402/pull/3840",
        "https://github.com/x402-foundation/x402",
        "https://github.com/x402-foundation/x402/blob/go/v2.28.0/go/extensions/signinwithx/server.go",
        "https://github.com/x402-foundation/x402/blob/npm-@x402/extensions@v2.28.0/typescript/packages/extensions/src/sign-in-with-x/hooks.ts",
        "https://github.com/x402-foundation/x402/blob/pypi-x402@v2.25.0/python/x402/extensions/sign_in_with_x/hooks.py"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-639"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/113xxx/CVE-2026-113603.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-113603",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 499643,
  "published_at": "2026-10-20T15:40:30.742+00:00"
}