November 14, 2026

CVE Watchtower

CVE-2026-63634tempoxyz pympp Improper Input Validation

NVD

Vulnerability Summary

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 Γ— 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 Level
MEDIUM(6.9)
Published Date
Nov 9, 2026
Last Modified
Nov 12, 2026
Exploitation Status
No confirmed exploitation yet
EPSS Score (30-Day)
0.29%Probability
Root Weakness (CWE)
CWE-20: Improper Input Validation β†—
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required.
CVSS v4.0 Base Metrics — Score 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
Attack VectorNetwork
Attack ComplexityLow
Attack RequirementsNone
Privileges RequiredNone
User InteractionNone
Confidentiality (Vulnerable System)None
Integrity (Vulnerable System)Low
Availability (Vulnerable System)None
Confidentiality (Subsequent System)None
Integrity (Subsequent System)None
Availability (Subsequent System)None

Affected & Patched Versions

Affected Versions
  • tempoxyz pympp < 0.9.1
Patched Versions
No patched version published yet
Until a fix ships, reduce exposure:
  • Restrict access to the affected service or interface to trusted networks.
  • Disable the affected feature if you do not need it.
  • Watch the vendor advisory for a firmware or software update.

What to do

Fix it during your normal patch cycle. No exploitation is confirmed yet.

  1. Check whether you run tempoxyz pympp and which version.
  2. No patched version is listed yet. Limit access to the affected service to trusted networks, and disable the feature if you can.
  3. Subscribe to the vendor advisory so you learn when a fix ships.

Timeline

  • Nov 9, 2026Published
  • Nov 12, 2026Record last modified

Score, severity and exploitation changes are tracked from the day Watchtower started logging them.

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External References

Data last checked: Nov 13, 2026 21:28 UTC