ZenHive mpp up to 0.16.0 FeePayerPolicy fee_payer_policy.ex MPP.Methods.Tempo.FeePayerPolicy.measure input validation

Summaryinfo

A vulnerability classified as critical has been found in ZenHive mpp up to 0.16.0. The impacted element is the function MPP.Methods.Tempo.FeePayerPolicy.measure of the file lib/mpp/methods/tempo/fee_payer_policy.ex of the component FeePayerPolicy. The manipulation leads to input validation. This vulnerability is documented as CVE-2026-82750. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in ZenHive mpp up to 0.16.0 and classified as critical. This issue affects the function MPP.Methods.Tempo.FeePayerPolicy.measure of the file lib/mpp/methods/tempo/fee_payer_policy.ex of the component FeePayerPolicy. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-82750 since 08/31/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available.

Upgrading to version 0.16.1 eliminates this vulnerability.

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Productinfo

Vendor

• ZenHive

Name

• mpp

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10
• 0.11
• 0.12
• 0.13
• 0.14
• 0.15
• 0.16.0

Website

• Product: https://github.com/ZenHive/mpp/

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