mppx: Gas Draining with access list

[ Why it matters ]Priority signals

• Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

mppx is a TypeScript interface for machine payments protocol. Prior to 0.8.2, the fee-payer cosigning path in src/tempo/internal/fee-payer.ts copied a client-supplied access_list from a 0x78 FeePayerEnvelope without validating its length or contents. Because EIP-2930 access-list entries consume intrinsic gas even when the listed addresses are never used, a client could add fabricated address-only entries and cause the server fee_payer wallet to pay unnecessary transaction fees. The demonstrated 180-entry list remained within the 500,000 gas policy cap, 16 KB header limit, and RPC simulation budget while increasing the fee by approximately 9.4 times. 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 < 0.8.2)

[ Packages ]Affected open-source packages

• mppx npmAffected < 0.8.2 · fixed in 0.8.2 · GHSA-vc9j-9wph-qghj

[ References ]References

• github.com/wevm/mppx/security/advisories/GHSA-vc9j-9wph-qghjx_refsource_CONFIRM
• github.com/wevm/mppx/pull/602x_refsource_MISC
• github.com/wevm/mppx/commit/24ddcca719ae282977d8747309ed1275ea282b25x_refsource_MISC
• github.com/wevm/mppx/releases/tag/mppx@0.8.2x_refsource_MISC