CVE-2026-73136
Fix: ZenHive/mpp@2207d7fCVE-2026-73136 is a CWE-294 vulnerability in mpp. O3 Security confirms whether CVE-2026-73136 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Static memo configuration in mpp Tempo disables per-challenge attribution binding, enabling third-party replay
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-73136.
Real-World Exposure
mppReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Hex packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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.
Workaround
Remove the static "memo" from the Tempo method_config so verification falls back to the default per-challenge attribution binding, which ties each settled transfer to the challenge being verified. Where a static memo must be kept, configure a dedup store (for example MPP.Tempo.ConCacheStore) with a TTL at least as long as the challenge expiry, which reduces unlimited replay to a race on the transaction hash rather than closing it.
Configuration
Only deployments that configure a static "memo" in the Tempo method_config are affected. Deployments using the default per-challenge attribution memo are not: that path binds each settled transfer to the challenge under verification and is single-use by construction.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💧Hex | mpp | ≥ 0.6.1&&< 0.6.4 | 0.6.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mpp. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update mpp to 0.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-73136 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-73136 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-73136. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-73136 in your dependencies?
O3 detects CVE-2026-73136 across Hex dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.