{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-73829", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-08-17T11:15:02.320Z", "datePublished": "2026-08-19T17:19:43.696Z", "dateUpdated": "2026-08-19T17:19:43.696Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.MPP.Methods.Tempo'"], "packageName": "mpp", "packageURL": "pkg:hex/mpp", "product": "mpp", "programFiles": ["lib/mpp/methods/tempo.ex"], "programRoutines": [{"name": "'Elixir.MPP.Methods.Tempo':verify/2"}], "repo": "https://github.com/ZenHive/mpp", "vendor": "ZenHive", "versions": [{"lessThan": "0.6.1", "status": "affected", "version": "0.2.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.MPP.Methods.Tempo'"], "packageName": "zenhive/mpp", "packageURL": "pkg:github/zenhive/mpp", "product": "mpp", "programFiles": ["lib/mpp/methods/tempo.ex"], "programRoutines": [{"name": "'Elixir.MPP.Methods.Tempo':verify/2"}], "repo": "https://github.com/ZenHive/mpp", "vendor": "ZenHive", "versions": [{"lessThan": "46c5b0e1311da7d92190dc7d9ea89027a1d365e9", "status": "affected", "version": "f8904666061fbab695874856d8fcd02c471dfe1b", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>The race is only reachable when <code>MPP.Methods.Tempo</code> is configured with a dedup store (<code>\"store\"</code> in <code>method_config</code>). The default is <code>nil</code>, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue.</p>"}, {"base64": false, "type": "text/markdown", "value": "The race is only reachable when `MPP.Methods.Tempo` is configured with a dedup store (`\"store\"` in `method_config`). The default is `nil`, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue."}], "value": "The race is only reachable when MPP.Methods.Tempo is configured with a dedup store (\"store\" in method_config). The default is nil, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*", "versionEndExcluding": "0.6.1", "versionStartIncluding": "0.2.0", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "AND"}], "credits": [{"lang": "en", "type": "analyst", "value": "Jonatan M\u00e4nnchen / EEF"}, {"lang": "en", "type": "finder", "value": "E.FU"}, {"lang": "en", "type": "remediation developer", "value": "E.FU"}], "datePublic": "2026-06-29T00:00:00.000Z", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.</p>\n<p>The <code>type=\"hash\"</code> credential path in <code>MPP.Methods.Tempo.verify/2</code> guards against replay with a non-atomic check-then-mark sequence: <code>check_hash_unused/2</code> reads the dedup store, an <code>eth_getTransactionReceipt</code> round trip verifies the payment on chain, and only then does <code>mark_hash_used/2</code> write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic <code>check_and_mark/2</code> primitive is available and used by the <code>type=\"transaction\"</code> path, but the hash path calls plain <code>get</code> and <code>put</code> even when the configured store implements it. Exploitation requires a dedup store to be configured; the default <code>nil</code> store is stateless and documented as offering no replay protection at all.</p>\n<p>This issue affects mpp: from 0.2.0 before 0.6.1.</p>"}, {"base64": false, "type": "text/markdown", "value": "Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.\n\nThe `type=\"hash\"` credential path in `MPP.Methods.Tempo.verify/2` guards against replay with a non-atomic check-then-mark sequence: `check_hash_unused/2` reads the dedup store, an `eth_getTransactionReceipt` round trip verifies the payment on chain, and only then does `mark_hash_used/2` write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic `check_and_mark/2` primitive is available and used by the `type=\"transaction\"` path, but the hash path calls plain `get` and `put` even when the configured store implements it. Exploitation requires a dedup store to be configured; the default `nil` store is stateless and documented as offering no replay protection at all.\n\nThis issue affects mpp: from 0.2.0 before 0.6.1."}], "value": "Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.\n\nThe type=\"hash\" credential path in MPP.Methods.Tempo.verify/2 guards against replay with a non-atomic check-then-mark sequence: check_hash_unused/2 reads the dedup store, an eth_getTransactionReceipt round trip verifies the payment on chain, and only then does mark_hash_used/2 write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic check_and_mark/2 primitive is available and used by the type=\"transaction\" path, but the hash path calls plain get and put even when the configured store implements it. Exploitation requires a dedup store to be configured; the default nil store is stateless and documented as offering no replay protection at all.\n\nThis issue affects mpp: from 0.2.0 before 0.6.1."}], "impacts": [{"capecId": "CAPEC-29", "descriptions": [{"lang": "en", "value": "CAPEC-29 Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions"}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 6.3, "baseSeverity": "MEDIUM", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-367", "description": "CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-08-19T17:19:43.696Z"}, "references": [{"tags": ["vendor-advisory", "related"], "url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-w8j7-7qc3-5f24"}, {"tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-73829.html"}, {"tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-73829"}, {"tags": ["patch"], "url": "https://github.com/ZenHive/mpp/commit/46c5b0e1311da7d92190dc7d9ea89027a1d365e9"}], "source": {"discovery": "EXTERNAL"}, "title": "Non-atomic hash-credential dedup in mpp Tempo allows replay of a confirmed payment under a concurrent race"}}}

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