ZenHive mpp up to 0.16.0 FeePayerPolicy fee_payer_policy.ex MPP.Methods.Tempo.FeePayerPolicy.measure improper authorization

Summaryinfo

A vulnerability classified as critical was found in ZenHive mpp up to 0.16.0. This 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 results in improper authorization. This vulnerability is reported as CVE-2026-82751. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in ZenHive mpp up to 0.16.0. It has been classified as critical. Affected 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 with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-82751 since 08/31/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1548.002 by the MITRE ATT&CK project.

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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