CVE-2026-59695
HighCVSS 8.3Exploitation Probability (EPSS)
Low risk22th percentile - higher than 22% of all known CVEs
Summary
A vulnerability in the ZenHive mpp library allows an unauthenticated remote attacker to drain the fee-payer wallet in a single request by specifying an arbitrarily high gas price. The library does not validate the max_fee_per_gas and max_priority_fee_per_gas fields before co-signing the transaction, causing the server's wallet to be charged inflated costs.
Risk Assessment
The risk is the complete loss of funds from the fee-payer wallet, preventing the server from sponsoring gas for legitimate payment requests and leading to service disruption.
Recommendation
Immediately upgrade the mpp library to version 0.6.0 or later, which includes a fix that validates reasonable limits for gas prices before signing transactions.
Other vulnerabilities in mpp
See all- CVE-2026-59694High
A vulnerability in the mpp library (ZenHive) allows an unauthenticated remote client to inflate the fee-payer's gas cost by adding a large number of fabricated EIP-2930 access list entries. The server co-signs the transaction without validating the list length or contents, leading to a multiple increase in gas costs.
- CVE-2026-59252High
A vulnerability in the mpp library (ZenHive) allows an unauthenticated remote client to drain the fee-payer wallet by submitting EVM transactions with a deliberately low gas limit. The server co-signs and broadcasts the transaction, which fails due to out-of-gas, but the fee-payer wallet is charged for the burned gas while the attacker pays nothing. This leads to denial of service for legitimate clients as the fee-payer wallet runs out of funds.
Original NVD description (English source)
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.