{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-82750", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-08-31T01:00:09.774Z", "datePublished": "2026-09-06T16:08:41.089Z", "dateUpdated": "2026-09-06T16:08:41.089Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.MPP.Methods.Tempo.FeePayerPolicy'", "'Elixir.MPP.Methods.Tempo'"], "packageName": "mpp", "packageURL": "pkg:hex/mpp", "product": "mpp", "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", "versions": [{"lessThan": "0.16.1", "status": "affected", "version": "0.2.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.MPP.Methods.Tempo.FeePayerPolicy'", "'Elixir.MPP.Methods.Tempo'"], "packageName": "zenhive/mpp", "packageURL": "pkg:github/zenhive/mpp", "product": "mpp", "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", "versions": [{"lessThan": "0482572b47e1ffe1537ab80ab613d47b92833c2d", "status": "affected", "version": "d29d54e507918db00a5b65d90136b73166c017d7", "versionType": "git"}]}], "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 M\u00e4nnchen / EEF"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>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.</p>\n<p>When the server sponsors Tempo payments, <code>MPP.Methods.Tempo.FeePayerPolicy.measure/3</code> in <code>lib/mpp/methods/tempo/fee_payer_policy.ex</code> bounds the gas fields, the fee budget, the validity window and the access list of the client-signed <code>0x76</code> envelope, but never reads its <code>aa_authorization_list</code> 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 <code>gas_limit</code> 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.</p>\n<p>This issue affects mpp: from 0.2.0 before 0.16.1.</p>"}, {"base64": false, "type": "text/markdown", "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."}], "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."}], "impacts": [{"capecId": "CAPEC-130", "descriptions": [{"lang": "en", "value": "CAPEC-130 Excessive Allocation"}]}], "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": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-09-06T16:08:41.089Z"}, "references": [{"tags": ["vendor-advisory", "related"], "url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-5qrp-r24c-w6jr"}, {"tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-82750.html"}, {"tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-82750"}, {"tags": ["patch"], "url": "https://github.com/ZenHive/mpp/commit/0482572b47e1ffe1537ab80ab613d47b92833c2d"}], "source": {"discovery": "EXTERNAL"}, "title": "Unbounded EIP-7702 authorization list in mpp Tempo fee-payer sponsorship inflates gas cost and sponsors account delegation", "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."}]}}}

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