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[ CVE-2026-63627 · Published 22 Sep 2026 ]

mppx: Gas Draining with padding

CVSS 6.9 EPSS <1%Fix available

[ Description ]Official description

mppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, FeePayerPolicy in src/tempo/internal/fee-payer.ts used decodeFunctionData to validate fee-sponsored calldata but did not reject trailing bytes. A client could append nonzero padding that increased intrinsic calldata gas while gas_limit and max_fee_per_gas remained within policy caps, causing the server fee_payer wallet to pay substantially more than the decoded transaction required. The tested 16 KB header limit bounded the demonstrated padding to about 5,500 bytes and produced approximately five times the normal transaction fee. This issue is fixed in version 0.8.2.

[ Fixes ]Fixes and patches

  • mppx 0.8.2Fixed version · GitHub Advisories · npm package mppx: upgrade to 0.8.2 or later (affected < 0.8.1)

[ Packages ]Affected open-source packages

[ References ]References