Fee-payer gas draining via unchecked access lists
Published Sep 22, 2026 · Updated Sep 22, 2026
Improper input validation in mppx before 0.8.2 allows remote attackers to inflate a server fee-payer wallet's transaction costs. The Tempo fee-payer cosigning path in src/tempo/internal/fee-payer.ts copies a client-supplied access_list from a 0x78 FeePayerEnvelope without checking its length or contents. A server must act as the fee payer; fabricated address-only entries consume intrinsic gas, and 180 entries raised the demonstrated fee by about 9.4 times without exceeding existing caps.
Summary
What happened
Improper input validation in mppx before 0.8.2 allows remote attackers to inflate a server fee-payer wallet's transaction costs. The Tempo fee-payer cosigning path in src/tempo/internal/fee-payer.ts copies a client-supplied access_list from a 0x78 FeePayerEnvelope without checking its length or contents. A server must act as the fee payer; fabricated address-only entries consume intrinsic gas, and 180 entries raised the demonstrated fee by about 9.4 times without exceeding existing caps.
The record
- CVE
- CVE-2026-63628
- Published
- Sep 22, 2026
- Updated
- Sep 22, 2026
- Vendor
- wevm
- Product
- mppx
- Classifications
- CWE-20
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 22, 2026CVE publishedPublication date reported by the CVE source.
- Sep 22, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 0.8.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
- mppx access-list gas-draining Docker proof of conceptfunctional · demonstrated
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Technologies
Your stack
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Your stack
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