mppx: Gas Draining with padding
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, 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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- 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-727h-3vm5-qwq6 |
- 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-727h-3vm5-qwq6
Remediation
- Fix · CNA mppx (wevm) Fixed in 0.8.2
- Fix · GHSA-727h-3vm5-qwq6 mppx (npm) Fixed in 0.8.2 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-63627
- 2026-10-03 Alias added: GHSA-727h-3vm5-qwq6
References
More wevm vulnerabilities
- TI-2026-45274 mppx: Gas Draining with access list CVSS 4.0MEDIUM 6.9
- TI-2026-26504 mppx: Tempo has a session close voucher bypass vulnerability due to settled amount equality CVSS 3.1HIGH 7.5
- TI-2026-26505 mppx has Stripe charge credential replay via missing idempotency check CVSS 4.0MEDIUM 6.0
Sources
- CVE-2026-63627 · CVE Program
- CVE-2026-63627 · NVD
- FIRST EPSS
- GHSA-727h-3vm5-qwq6 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences