---
id: CVE-2026-82751
title: >-
  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
  provisioning an acc…
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
  provisioning an acc…
severity: high
cvss: 8.3
cvssVector: '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'
cwe:
  - CWE-1284
vendor: ZenHive
product: mpp
affected:
  - mpp >= 0.2.0 < 0.16.1
  - >-
    zenhive/mpp >= d29d54e507918db00a5b65d90136b73166c017d7 <
    0482572b47e1ffe1537ab80ab613d47b92833c2d
published: '2026-09-06'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T19:20:01.390'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-82751'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-82751.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/ZenHive/mpp/commit/0482572b47e1ffe1537ab80ab613d47b92833c2d
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://github.com/ZenHive/mpp/security/advisories/GHSA-rpwj-vrf7-4x36'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-82751'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-08T18:24:07.502205Z'
cvssSource: cna
epss: 0.00524
epssPercentile: 0.41997
ingestedAt: '2026-09-07T06:06:09.687Z'
---

## Overview

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 provisioning an access key on the client's own account.

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 does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.