CVE-2026-73136 Static memo configuration in mpp Tempo disables per-challenge attribution binding, enabling third-party replay

High 8.2 Published 19 Aug 2026 Updated 19 Aug 2026

Attackers can bypass authentication and access paid resources by replaying transactions when static memo configuration is enabled in ZenHive mpp.

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

What is CVE-2026-73136?

CVE-2026-73136 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 third party to obtain paid resources by replaying a transfer settled by an unrelated payer.

MPP.Methods.Tempo normally binds a settled TIP-20 TransferWithMemo to the specific challenge under verification through an attribution nonce carried in the memo. When a static "memo" is configured in method_config, check_matched_memo_binding/3 returns the match unconditionally and that binding is skipped, leaving only token, recipient, amount and the static memo value to match on. The static memo is echoed in every unauthenticated 402 response and Tempo transfers are public, so an attacker can take any matching transfer paid by a legitimate customer, request a fresh challenge for the same route, and present that transaction hash as a type="hash" credential. The hash path performs no sender or signature check tying the presenter to the wallet that broadcast the transfer.

This issue affects mpp: from 0.6.1 before 0.6.4.

Weakness: CWE-294

Which versions are affected by CVE-2026-73136?

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

Package	Affected	Fixed in
`mpp` Hex	From `0.6.1`	`0.6.4`

Products include Zenhive Machine Payments Protocol.

How do I fix CVE-2026-73136?

Upgrade mpp to 0.6.4 or later.

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

Is CVE-2026-73136 being exploited?

There is no known exploitation of CVE-2026-73136 in the wild and no public exploit code.

Sources

Also known as EEF-CVE-2026-73136, GHSA-34g7-vx6g-82mq, GHSA-cw4v-5gcf-x3cw.