{"id":"CVE-2026-82750","state":"PUBLISHED","title":"Unbounded EIP-7702 authorization list in mpp Tempo fee-payer sponsorship inflates gas cost and sponsors account delegation","description":"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.\n\nWhen 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.\n\nThis issue affects mpp: from 0.2.0 before 0.16.1.","publishedAt":"2026-09-06T16:08:41.089Z","updatedAt":"2026-09-08T18:25:42.388Z","severity":{"score":8.3,"label":"High","version":"4.0","vector":"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","source":"EEF"},"assigner":"EEF","products":["ZenHive mpp"],"affected":[{"vendor":"ZenHive","product":"mpp","packageName":"mpp","packageURL":"pkg:hex/mpp","defaultStatus":"unaffected","versions":[{"version":"0.2.0","status":"affected","lessThan":"0.16.1","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MPP.Methods.Tempo.FeePayerPolicy'","'Elixir.MPP.Methods.Tempo'"],"programFiles":["lib/mpp/methods/tempo/fee_payer_policy.ex","lib/mpp/methods/tempo.ex"],"programRoutines":[{"name":"'Elixir.MPP.Methods.Tempo.FeePayerPolicy':measure/3"},{"name":"'Elixir.MPP.Methods.Tempo.FeePayerPolicy':validate/3"},{"name":"'Elixir.MPP.Methods.Tempo':verify/2"}],"repo":"https://github.com/ZenHive/mpp"},{"vendor":"ZenHive","product":"mpp","packageName":"zenhive/mpp","packageURL":"pkg:github/zenhive/mpp","defaultStatus":"unaffected","versions":[{"version":"d29d54e507918db00a5b65d90136b73166c017d7","status":"affected","lessThan":"0482572b47e1ffe1537ab80ab613d47b92833c2d","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MPP.Methods.Tempo.FeePayerPolicy'","'Elixir.MPP.Methods.Tempo'"],"programFiles":["lib/mpp/methods/tempo/fee_payer_policy.ex","lib/mpp/methods/tempo.ex"],"programRoutines":[{"name":"'Elixir.MPP.Methods.Tempo.FeePayerPolicy':measure/3"},{"name":"'Elixir.MPP.Methods.Tempo.FeePayerPolicy':validate/3"},{"name":"'Elixir.MPP.Methods.Tempo':verify/2"}],"repo":"https://github.com/ZenHive/mpp"}],"references":["https://github.com/ZenHive/mpp/security/advisories/GHSA-5qrp-r24c-w6jr","https://cna.erlef.org/cves/CVE-2026-82750.html","https://osv.dev/vulnerability/EEF-CVE-2026-82750","https://github.com/ZenHive/mpp/commit/0482572b47e1ffe1537ab80ab613d47b92833c2d"],"weaknesses":["CWE-1284"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/82xxx/CVE-2026-82750.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-82750","state":"PUBLISHED","datePublished":"2026-09-06T16:08:41.089Z","dateUpdated":"2026-09-08T18:25:42.388Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-08-31T01:00:09.774Z"},"containers":{"cna":{"title":"Unbounded EIP-7702 authorization list in mpp Tempo fee-payer sponsorship inflates gas cost and sponsors account delegation","descriptions":[{"lang":"en","value":"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.\n\nWhen 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.\n\nThis issue affects mpp: from 0.2.0 before 0.16.1."}],"affected":[{"vendor":"ZenHive","product":"mpp","packageName":"mpp","packageURL":"pkg:hex/mpp","defaultStatus":"unaffected","versions":[{"version":"0.2.0","status":"affected","lessThan":"0.16.1","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MPP.Methods.Tempo.FeePayerPolicy'","'Elixir.MPP.Methods.Tempo'"],"programFiles":["lib/mpp/methods/tempo/fee_payer_policy.ex","lib/mpp/methods/tempo.ex"],"programRoutines":[{"name":"'Elixir.MPP.Methods.Tempo.FeePayerPolicy':measure/3"},{"name":"'Elixir.MPP.Methods.Tempo.FeePayerPolicy':validate/3"},{"name":"'Elixir.MPP.Methods.Tempo':verify/2"}],"repo":"https://github.com/ZenHive/mpp"},{"vendor":"ZenHive","product":"mpp","packageName":"zenhive/mpp","packageURL":"pkg:github/zenhive/mpp","defaultStatus":"unaffected","versions":[{"version":"d29d54e507918db00a5b65d90136b73166c017d7","status":"affected","lessThan":"0482572b47e1ffe1537ab80ab613d47b92833c2d","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"],"modules":["'Elixir.MPP.Methods.Tempo.FeePayerPolicy'","'Elixir.MPP.Methods.Tempo'"],"programFiles":["lib/mpp/methods/tempo/fee_payer_policy.ex","lib/mpp/methods/tempo.ex"],"programRoutines":[{"name":"'Elixir.MPP.Methods.Tempo.FeePayerPolicy':measure/3"},{"name":"'Elixir.MPP.Methods.Tempo.FeePayerPolicy':validate/3"},{"name":"'Elixir.MPP.Methods.Tempo':verify/2"}],"repo":"https://github.com/ZenHive/mpp"}],"references":[{"url":"https://github.com/ZenHive/mpp/security/advisories/GHSA-5qrp-r24c-w6jr","tags":["vendor-advisory","related"]},{"url":"https://cna.erlef.org/cves/CVE-2026-82750.html","tags":["related"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-82750","tags":["related"]},{"url":"https://github.com/ZenHive/mpp/commit/0482572b47e1ffe1537ab80ab613d47b92833c2d","tags":["patch"]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":8.3,"baseSeverity":"HIGH","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"LOW","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1284","description":"CWE-1284 Improper Validation of Specified Quantity in Input","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"EEF","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateUpdated":"2026-09-06T16:08:41.089Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>Only deployments that enable Tempo server-side fee sponsorship are affected, through <code>\"fee_payer\" =&gt; true</code> in <code>method_config</code> with either local co-signing (<code>fee_payer_private_key</code>) or hosted sponsorship (<code>fee_payer_url</code>). Sponsorship is disabled by default.</p>"},{"base64":false,"type":"text/markdown","value":"Only deployments that enable Tempo server-side fee sponsorship are affected, through `\"fee_payer\" => true` in `method_config` with either local co-signing (`fee_payer_private_key`) or hosted sponsorship (`fee_payer_url`). Sponsorship is disabled by default."}],"value":"Only deployments that enable Tempo server-side fee sponsorship are affected, through \"fee_payer\" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default."}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*","versionEndExcluding":"0.16.1","versionStartIncluding":"0.2.0","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"AND"}],"credits":[{"lang":"en","type":"finder","value":"Kian Kai Ang"},{"lang":"en","type":"reporter","value":"Kian Kai Ang"},{"lang":"en","type":"remediation developer","value":"E.FU"},{"lang":"en","type":"coordinator","value":"Jonatan Männchen / EEF"}],"impacts":[{"capecId":"CAPEC-130","descriptions":[{"lang":"en","value":"CAPEC-130 Excessive Allocation"}]}],"source":{"discovery":"EXTERNAL"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>Disable Tempo fee sponsorship by leaving <code>\"fee_payer\"</code> at its default of <code>false</code> and setting no <code>fee_payer_url</code>, so the client pays its own gas. Where sponsorship must stay enabled, lower the <code>max_gas</code> override in <code>fee_payer_policy</code> to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.</p>"},{"base64":false,"type":"text/markdown","value":"Disable Tempo fee sponsorship by leaving `\"fee_payer\"` at its default of `false` and setting no `fee_payer_url`, so the client pays its own gas. Where sponsorship must stay enabled, lower the `max_gas` override in `fee_payer_policy` to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it."}],"value":"Disable Tempo fee sponsorship by leaving \"fee_payer\" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it."}]},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-08T18:25:27.116993Z","id":"CVE-2026-82750","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-08T18:25:42.388Z"}}]}}}