Unbounded EIP-7702 authorization list in mpp Tempo fee-payer sponsorship inflates gas cost and sponsors account delegation

{
  "id": "595d54d051a32c310a013d0dcdd02f1a157d68a254dfa7a445d2c67128ccdb76",
  "url": "https://osv.dev/vulnerability/CVE-2026-82750",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Unbounded EIP-7702 authorization list in mpp Tempo fee-payer sponsorship inflates gas cost and sponsors account delegation",
    "summary": "Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing. When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense. This issue affects mpp: from 0.2.0 before 0.16.1.",
    "evidence": "osv:CVE-2026-82750",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-82750",
      "aliases": [
        "CVE-2026-82750",
        "EEF-CVE-2026-82750",
        "GHSA-5qrp-r24c-w6jr"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/zenhive/mpp",
              "type": "GIT",
              "events": [
                {
                  "introduced": "7ca7538f05959a98e0e5e63e4bd949b4f362cf8d"
                },
                {
                  "fixed": "4e9338ec02957f0140127b3c210fa8fff4df656a"
                },
                {
                  "fixed": "0482572b47e1ffe1537ab80ab613d47b92833c2d"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0.2.0"
                      },
                      {
                        "fixed": "0.16.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0482572b47e1ffe1537ab80ab613d47b92833c2d"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v0.16.0",
            "v0.15.0",
            "v0.14.0",
            "v0.13.0",
            "v0.12.0",
            "v0.11.0",
            "v0.10.0",
            "v0.9.0",
            "v0.8.0",
            "v0.7.0",
            "v0.6.4",
            "v0.6.3",
            "v0.6.1",
            "v0.6.0",
            "v0.5.1",
            "v0.4.0",
            "v0.3.0",
            "v0.2.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-82750.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.442730643Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-82750.html",
        "https://github.com",
        "https://osv.dev/vulnerability/EEF-CVE-2026-82750",
        "https://repo.hex.pm",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82750.json",
        "https://github.com/ZenHive/mpp/security/advisories/GHSA-5qrp-r24c-w6jr",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-82750",
        "https://github.com/ZenHive/mpp/commit/0482572b47e1ffe1537ab80ab613d47b92833c2d",
        "https://github.com/ZenHive/mpp"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1284"
        ],
        "cna_assigner": "EEF",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82750.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-82750",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 521306,
  "published_at": "2026-09-06T16:08:41.089+00:00"
}