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CVE-2026-63634

6.9 mediumEPSS 0.3%

Medium (6.9) in tempoxyz pympp. EPSS 0.3% estimated probability of exploitation activity in the next 30 days.

On this page
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.

Severity

CVSS 4.0

6.9 medium
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
EPSS
0.3% estimated probability of exploitation activity in the next 30 days; 22nd percentile. Scored 2026-11-10. A forecast for this CVE across the internet, not for your own systems.
CWE
CWE-20 Improper Input Validation
OWASP Top 10
A05:2025 Injection
Published
Assigned by
GitHub_M (CNA)
NVD analysis
Not in the NVD yet
Record from
the CVE List, synced

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Affected

Versions

From the CNA's record in the CVE List.

ProductAffected
tempoxyz pympp< 0.9.1

Attack patterns (CAPEC)

The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits. More on the page of CWE-20 (51).

References

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