MEDIUMCVSS v4 6.9Vulnerability
CVE-2026-63634
pympp is a Python SDK for the Machine Payments Protocol. Prior to version 0.9.1, when the server acts as the fee_payer, pympp validates calldata using eth_abi decoding, which is lenient about trailing bytes. The FeePayerPolicy caps gas_limit (≤ 2 M) and max_fee_per_gas (≤ 100 Gwei) but does not check calldata length. Tempo uses legacy calldata gas pricing: 16 gas per non-zero byte. Appending N bytes of 0x01 padding inflates actual gas used by N × 16 while keeping gas_limit and max_fee_per_gas within policy caps. The server cosigns and broadcasts the padded transaction, draining its fee-payer wallet. This issue has been patched in version 0.9.1.
Properties
- Severity
- MEDIUM
- Nvd fetched at
- 2026-11-10T23:33:48.924589+00:00
- Epss score
- 0.00291
- Cvss severity
- MEDIUM
- Cvss score
- 6.9
- Retrieved at
- 2026-11-10T23:35:19+00:00
- Last source
- FIRST EPSS
- Score
- 6.9
- Cvss version
- 4.0
- Cve id
- CVE-2026-63634
- Cvss vector
- CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- First seen by Signal
- 2026-11-10T03:20:43+00:00
- Vector
- CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- Published at
- 2026-11-09T22:18:53.803
- Last modified
- 2026-11-09T22:18:53.803
- Epss percentile
- 0.21919
Related Entities (1)
HAS_WEAKNESS (1)
Related research
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