CVE-2026-67581

On-chain transfer proof is not single-use in mpp EVM payment method, enabling cross-challenge replay

Published Aug 19, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
Description
Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer.

MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer.

This issue affects mpp: from 0.3.0 before 0.6.3.

Remediation

Vendor Workaround

Price each challenge uniquely (per-challenge or single-use amounts) so that a historical transfer cannot match a later charge, and keep challenge expiry short to narrow the window in which any given transfer stays useful. Deployments that can use the Tempo method for on-chain payments get per-challenge attribution binding instead.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Zenhive machine Payments Protocol
CPEs cpe:2.3:a:zenhive:machine_payments_protocol:*:*:*:*:*:elixir:*:*
Vendors & Products Zenhive machine Payments Protocol
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}

Type Values Removed Values Added
First Time appeared Zenhive
Zenhive mpp
Vendors & Products Zenhive
Zenhive mpp
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer. MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer. This issue affects mpp: from 0.3.0 before 0.6.3.
Title On-chain transfer proof is not single-use in mpp EVM payment method, enabling cross-challenge replay
First Time appeared Zenhive
Zenhive mpp
Weaknesses CWE-294
CPEs cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*
Vendors & Products Zenhive
Zenhive mpp
References
Metrics cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
EEF
Published
Updated
Aug 19, 2026, 6:44 PM
Reserved
Aug 18, 2026, 10:30 AM
Status
Analyzed
Published
Aug 19, 2026, 6:17 PM
Modified
Sep 10, 2026, 6:00 PM