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

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

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Aug 2026
- **Updated:** 19 Aug 2026
- **Also known as:** EEF-CVE-2026-73136, GHSA-34g7-vx6g-82mq, GHSA-cw4v-5gcf-x3cw

## 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 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2026-73136?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mpp` | Hex | From 0.6.1 | 0.6.4 |

Products: Zenhive Machine Payments Protocol.

## How do I fix CVE-2026-73136?

Upgrade mpp to 0.6.4 or later.

## Is CVE-2026-73136 being exploited?

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

## Other vulnerabilities in ZenHive mpp

- [CVE-2026-67581](https://insights.sbomify.com/CVE-2026-67581/): On-chain transfer proof is not single-use in mpp EVM payment method, enabling cross-challenge replay (high 8.7)
- [CVE-2026-73541](https://insights.sbomify.com/CVE-2026-73541/): Denial of service in mpp (high 8.3)
- [CVE-2026-73829](https://insights.sbomify.com/CVE-2026-73829/): Non-atomic hash-credential dedup in mpp Tempo allows replay of a confirmed payment under a concurrent race (medium 6.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-73136 and fix it if it is affected.

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

Affected packages and fixed versions:
- mpp (Hex): affected from 0.6.1; fixed in 0.6.4

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-73136/ (Markdown: https://insights.sbomify.com/CVE-2026-73136/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-73136
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-73136
- OSV: https://osv.dev/vulnerability/CVE-2026-73136

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-73136/
Summaries are generated and may contain mistakes; the official description above is the record.