mppx: Gas Draining with access list
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| wevm | mppx | before 0.8.2 | 0.8.2 | Patch available | CNA |
| — | mppx (npm) | before 0.8.2 | 0.8.2 | Patch available | GHSA-vc9j-9wph-qghj |
- mppx Vendorwevm Affected before 0.8.2 Fixed in 0.8.2 Patch available CNA
- mppx (npm) Vendor— Affected before 0.8.2 Fixed in 0.8.2 Patch available GHSA-vc9j-9wph-qghj
Remediation
- Fix · CNA mppx (wevm) Fixed in 0.8.2
- Fix · GHSA-vc9j-9wph-qghj mppx (npm) Fixed in 0.8.2 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-63628
- 2026-10-03 Alias added: GHSA-vc9j-9wph-qghj
References
More wevm vulnerabilities
- TI-2026-26504 mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality CVSS 3.1HIGH 7.5
- TI-2026-45273 mppx: Gas Draining with padding CVSS 4.0MEDIUM 6.9
- TI-2026-26505 mppx has Stripe charge credential replay via missing idempotency check CVSS 4.0MEDIUM 6.0
Sources
- CVE-2026-63628 · CVE Program
- CVE-2026-63628 · NVD
- FIRST EPSS
- GHSA-vc9j-9wph-qghj · GitHub Advisory Database · CC BY 4.0
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