CVE-2026-59695
Description
Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet in a single request by naming an arbitrarily high gas price. When 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 max_fee_per_gas and max_priority_fee_per_gas, without validating that they are within reasonable bounds. A malicious client embeds arbitrarily large values for these fields in the signed envelope. The server co-signs and broadcasts the transaction. The effective_gas_price billed against the fee-payer wallet is derived from the attacker-supplied ceilings, so the server pays those inflated per-gas rates out of its own wallet. A single crafted request can drain the wallet entirely, after which the server can no longer sponsor gas for legitimate payment requests. This issue affects mpp: from 0.2.0 before 0.6.0.
How to fix
- ZenHive mpp0.6.0, 5d6338e2334084c5f2a78cfcca474830733ed7e8 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| ZenHive mpp | 0.2.0 ≤ v < 0.6.0, d29d54e507918db00a5b65d90136b73166c017d7 ≤ v < 5d6338e2334084c5f2a78cfcca474830733ed7e8 | 0.6.0, 5d6338e2334084c5f2a78cfcca474830733ed7e8 |
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