{"id":"EEF-CVE-2026-73541","summary":"Tempo fee sponsorship in mpp bounds each transaction but not aggregate exposure, allowing concurrent sponsor-wallet drain","details":"## Summary\n\nAllocation 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.\n\n`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 \u003c= 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.\n\nThis issue affects mpp: from 0.2.0 before 0.12.0.\n\n## Workarounds\n\nDisable Tempo fee sponsorship by setting `\"fee_payer\" =\u003e false` (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering `max_total_fee` and `max_validity_window_seconds` reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.\n\n## Configurations\n\nOnly deployments that enable Tempo server-side fee sponsorship are affected, through `\"fee_payer\" =\u003e true` in `method_config` with either local co-signing (`fee_payer_private_key`) or hosted sponsorship (`fee_payer_url`). Sponsorship is disabled by default.","aliases":["CVE-2026-73541","GHSA-j4j7-7xpr-c7cr"],"modified":"2026-09-08T05:45:02.681764011Z","published":"2026-08-19T17:20:00.286Z","database_specific":{"capec_ids":["CAPEC-130"],"cpe_ids":["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-770"]},"references":[{"type":"ADVISORY","url":"https://github.com/ZenHive/mpp/security/advisories/GHSA-j4j7-7xpr-c7cr"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-73541.html"},{"type":"FIX","url":"https://github.com/ZenHive/mpp/commit/ddc46868fba57ccebb567c04709812b466123076"},{"type":"PACKAGE","url":"https://hex.pm/packages/mpp"}],"affected":[{"package":{"name":"mpp","ecosystem":"Hex","purl":"pkg:hex/mpp"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.2.0"},{"fixed":"0.12.0"}]}],"versions":["0.10.0","0.11.0","0.2.0","0.3.0","0.3.1","0.3.2","0.4.0","0.6.0","0.6.1","0.6.2","0.6.3","0.6.4","0.7.0","0.8.0","0.9.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-73541.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/ZenHive/mpp","events":[{"introduced":"d29d54e507918db00a5b65d90136b73166c017d7"},{"fixed":"ddc46868fba57ccebb567c04709812b466123076"}]}],"versions":["v0.11.0","v0.10.0","v0.9.0","v0.8.0","v0.7.0","v0.6.4","v0.6.3","v0.6.1","v0.6.0","v0.5.1","v0.4.0","v0.3.0","v0.2.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-73541.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}],"credits":[{"name":"E.FU","type":"FINDER"},{"name":"E.FU","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"ANALYST"}]}