ZenHive mpp CVE-2026-82750

The target must be running ZenHive mpp 0.2.0-0.16.0 with the MPP.Methods.Tempo payment sponsorship feature active and exposed to network clients. No authentication is required on the sponsorship endpoint itself - the vulnerable code path executes for any client-submitted 0x76 envelope. The CVSS 4.0 AT:P prerequisite is satisfied whenever a Tempo sponsorship service is deployed; servers not offering this feature are unaffected. The per-request gas cost multiplication is bounded by the server's configured gas_limit ceiling (limiting total financial loss per request), but within that ceiling an attacker can achieve the full ~40x amplification with seven delegation entries. There is no rate-limiting or client identification in the vulnerable code, so an attacker can submit requests repeatedly. The persistent EIP-7702 delegation side-effect requires no additional privilege beyond submitting a valid (but malicious) sponsorship request.

The CVSS 4.0 base score of 8.3 with vector AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L correctly characterises the threat. The AT:P (attack prerequisites) metric acknowledges that an MPP Tempo sponsorship service must be actively running - the sole prerequisite - after which any unauthenticated remote client can exploit the bypass with no complexity. The dual impact distinguishes this from a simple DoS: gas cost inflation drains the sponsor's on-chain budget at each request, while persistent EIP-7702 set-code delegations are effectively irreversible on-chain without further transactions and at further cost. Even a mid-sized municipal IT team in malbork operating a blockchain payment gateway built on mpp should treat this as urgent given the direct financial exposure and the difficulty of unwinding persistent account delegations. No EPSS data or CISA KEV listing is present in the provided intelligence; no public exploit code has been identified. The narrow deployment population (Elixir services actively sponsoring EIP-7702 Tempo payments) limits broad automated scanning, but any such deployment faces direct and quantifiable financial harm with each malicious request, constrained only by the configured gas_limit ceiling.

An unauthenticated attacker with network access to an MPP Tempo sponsorship service constructs a 0x76 transaction envelope populated with seven EIP-7702 authorization entries signed by throwaway private keys, then submits it to the sponsorship endpoint. The server validates gas limits, fee budget, and access list but accepts the aa_authorization_list unchecked, co-signs the envelope, and pays roughly 1.88M gas instead of 46,575 - a ~40x inflation - while the EIP-7702 delegations are written on-chain as persistent set-code operations on the attacker's addresses at the sponsor's expense.