{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-59694", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-07-06T14:05:47.003Z", "datePublished": "2026-07-17T10:11:49.192Z", "dateUpdated": "2026-07-17T10:11:49.192Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.MPP.Tempo.Transaction'"], "packageName": "mpp", "packageURL": "pkg:hex/mpp", "product": "mpp", "programFiles": ["lib/mpp/tempo/transaction.ex"], "programRoutines": [{"name": "'Elixir.MPP.Tempo.Transaction':cosign_fee_payer/3"}], "repo": "https://github.com/ZenHive/mpp", "vendor": "ZenHive", "versions": [{"lessThan": "0.6.0", "status": "affected", "version": "0.2.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.MPP.Tempo.Transaction'"], "packageName": "ZenHive/mpp", "packageURL": "pkg:github/ZenHive/mpp", "product": "mpp", "programFiles": ["lib/mpp/tempo/transaction.ex"], "programRoutines": [{"name": "'Elixir.MPP.Tempo.Transaction':cosign_fee_payer/3"}], "repo": "https://github.com/ZenHive/mpp", "vendor": "ZenHive", "versions": [{"lessThan": "5d6338e2334084c5f2a78cfcca474830733ed7e8", "status": "affected", "version": "d29d54e507918db00a5b65d90136b73166c017d7", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>The vulnerable code path is only reachable when the <tt>MPP.Methods.Tempo</tt> method is configured with <tt>fee_payer: true</tt> (server-side gas sponsorship). Default deployments with <tt>fee_payer: false</tt> are not affected, since the client pays for gas out of its own wallet.</p>"}], "value": "The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*", "versionEndExcluding": "0.6.0", "versionStartIncluding": "0.2.0", "vulnerable": true}], "negate": false, "operator": "AND"}], "operator": "OR"}], "credits": [{"lang": "en", "type": "finder", "value": "Kian Kai Ang"}, {"lang": "en", "type": "remediation developer", "value": "E.FU"}, {"lang": "en", "type": "analyst", "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 payment by a large multiplier, degrading the sponsor's operating margin.</p><p>When the <tt>mpp</tt> Elixir library is configured as fee payer (<tt>fee_payer: true</tt>), <tt>MPP.Tempo.Transaction.cosign_fee_payer/3</tt> re-signs the client-supplied base fields of the <tt>0x76</tt> AASigned envelope verbatim, including the EIP-2930 access list, without validating its length or contents. EIP-2930 access list entries incur intrinsic gas (~2,400 gas per address, plus 1,900 gas per storage key) charged before any opcode executes, regardless of whether the listed addresses are ever touched. A malicious client submits a valid <tt>transferWithMemo</tt> call alongside a large number of fabricated access-list entries. The server co-signs and broadcasts the transaction. The intended transfer executes normally, but the fee-payer wallet pays a large multiple of the expected gas cost with no corresponding on-chain work.</p><p>At the maintainer's default of 137 access-list entries (fitting within Bandit's 10,000-byte per-header-field limit) and 100 Gwei <tt>max_fee_per_gas</tt>, per-payment gas cost rises from ~51,287 to ~380,087 gas, a 7.4x multiplier. Sustained abuse destroys the sponsor's operating margin on low-cost payments and, over time, drains the fee-payer wallet.</p><p>This issue affects mpp: from 0.2.0 before 0.6.0.</p>"}], "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 payment by a large multiplier, degrading the sponsor's operating margin.\n\nWhen the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including the EIP-2930 access list, without validating its length or contents. EIP-2930 access list entries incur intrinsic gas (~2,400 gas per address, plus 1,900 gas per storage key) charged before any opcode executes, regardless of whether the listed addresses are ever touched. A malicious client submits a valid transferWithMemo call alongside a large number of fabricated access-list entries. The server co-signs and broadcasts the transaction. The intended transfer executes normally, but the fee-payer wallet pays a large multiple of the expected gas cost with no corresponding on-chain work.\n\nAt the maintainer's default of 137 access-list entries (fitting within Bandit's 10,000-byte per-header-field limit) and 100 Gwei max_fee_per_gas, per-payment gas cost rises from ~51,287 to ~380,087 gas, a 7.4x multiplier. Sustained abuse destroys the sponsor's operating margin on low-cost payments and, over time, drains the fee-payer wallet.\n\nThis issue affects mpp: from 0.2.0 before 0.6.0."}], "impacts": [{"capecId": "CAPEC-130", "descriptions": [{"lang": "en", "value": "CAPEC-130 Excessive Allocation"}]}], "metrics": [{"cvssV4_0": {"attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 8.3, "baseSeverity": "HIGH", "privilegesRequired": "NONE", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "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"}, "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": "2026-07-17T10:11:49.192Z"}, "references": [{"tags": ["vendor-advisory", "related"], "url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-qpxh-ff8m-c62v"}, {"tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-59694.html"}, {"tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-59694"}, {"tags": ["patch"], "url": "https://github.com/ZenHive/mpp/commit/5d6338e2334084c5f2a78cfcca474830733ed7e8"}], "source": {"discovery": "EXTERNAL"}, "title": "Unbounded access list in mpp Tempo fee-payer inflates gas cost per payment", "x_generator": {"engine": "cvelib 1.8.0"}}}}

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