CVE-2026-67581 On-chain transfer proof is not single-use in mpp EVM payment method, enabling cross-challenge replay

High 8.7 Published 19 Aug 2026 Updated 19 Aug 2026

Attackers can replay settled on-chain transfers to bypass payment verification and access paid resources in ZenHive mpp EVM payment methods.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-67581?

CVE-2026-67581 is a high-severity authentication bypass vulnerability in ZenHive mpp, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-294

Which versions are affected by CVE-2026-67581?

1 open source package ship an affected version, including mpp. It affects 1 product.

Package	Affected	Fixed in
`mpp` Hex	From `0.3.0`	`0.6.3`

Products include Zenhive Machine Payments Protocol.

How do I fix CVE-2026-67581?

Upgrade mpp to 0.6.3 or later.

Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.

Is CVE-2026-67581 being exploited?

There is no known exploitation of CVE-2026-67581 in the wild and no public exploit code.

Sources

Also known as EEF-CVE-2026-67581, GHSA-vp5h-xh25-44wf, GHSA-vrg5-xm7q-qcjh.