Is there a public exploit for CVE-2026-63634?

No public exploit for CVE-2026-63634 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-63634?

CVE-2026-63634 scores CVSS 6.9 (v4.0), rated medium. EPSS puts the chance of exploitation in the next 30 days at 0.29%.

What does CVE-2026-63634 affect?

CVE-2026-63634 affects tempoxyz pympp.

6.9 Medium

pympp is a Python SDK for the Machine Payments Protocol.

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 feepayer, pympp validates calldata using ethabi decoding, which is lenient about trailing bytes. The FeePayerPolicy caps gaslimit (≤ 2 M) and maxfeepergas (≤ 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 gaslimit and maxfeepergas 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.

Assessment

CVSS: 6.9 (v4.0)
Severity: Medium
EPSS: 0.29% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 9 November 2026
Last updated: 12 November 2026
Affected: tempoxyz · pympp
Assigner: GitHub_M

CVSS vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

At the source

EUVD (ENISA)

References

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