{"id":"CVE-2026-73829","aliases":["EEF-CVE-2026-73829","EUVD-2026-62591","GHSA-vjfr-ffhr-5g8p","GHSA-w8j7-7qc3-5f24"],"status":"published","title":"Non-atomic hash-credential dedup in mpp Tempo allows replay of a confirmed payment under a concurrent race","description":"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.","severity":{"version":"4.0","score":6.3,"vector":"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00323,"percentile":0.2561,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-367"],"published":"2026-08-19T17:19:43Z","modified":"2026-10-28T02:30:54Z","fixes":[{"ecosystem":"Hex","package":"mpp","fixed_in":["0.6.1"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Hex","package":"mpp","ranges":[{"type":"SEMVER","events":[{"introduced":"0.2.0"},{"fixed":"0.6.1"}]}],"versions":["0.2.0","0.3.0","0.3.1","0.3.2","0.4.0","0.6.0"]}],"products":[{"vendor":"zenhive","product":"machine_payments_protocol"},{"vendor":"zenhive","product":"mpp"}],"references":[{"url":"https://github.com/ZenHive/mpp/security/advisories/GHSA-w8j7-7qc3-5f24","tags":["vendor-advisory","related","Vendor Advisory","advisory"]},{"url":"https://cna.erlef.org/cves/CVE-2026-73829.html","tags":["related","Third Party Advisory","web"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-73829","tags":["related","Third Party Advisory","web"]},{"url":"https://github.com/ZenHive/mpp/commit/46c5b0e1311da7d92190dc7d9ea89027a1d365e9","tags":["patch","Patch","fix"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-73829","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-vjfr-ffhr-5g8p"},{"url":"https://github.com","tags":["web"]},{"url":"https://repo.hex.pm","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73829.json","tags":["advisory"]},{"url":"https://github.com/ZenHive/mpp","tags":["package"]},{"url":"https://hex.pm/packages/mpp","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-73829","title":"Non-atomic hash-credential dedup in mpp Tempo allows replay of a confirmed payment under a concurrent race","description":"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.","status":"published","published":"2026-08-19T17:19:43.696Z","modified":"2026-08-19T18:58:33.322Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium","assessor":"cna"}],"cwes":["CWE-367"],"updated_at":"2026-11-02T13:43:33.766176Z"}],"euvd":[{"id":"EUVD-2026-62591","description":"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.","status":"published","published":"2026-08-19T17:19:43Z","modified":"2026-08-19T18:58:33Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium"}],"updated_at":"2026-11-02T18:01:40.9092Z"}],"ghsa":[{"id":"GHSA-vjfr-ffhr-5g8p","title":"Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote...","description":"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.","status":"published","published":"2026-08-19T18:32:54Z","modified":"2026-09-10T18:33:06Z","cvss":[{"version":"4.0","score":6.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"},{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"low"}],"cwes":["CWE-367"],"updated_at":"2026-11-02T15:11:42.667371Z"}],"nvd":[{"id":"CVE-2026-73829","description":"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.","status":"published","published":"2026-08-19T18:17:25.8Z","modified":"2026-09-10T18:30:09.27Z","cvss":[{"version":"4.0","score":6.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"},{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"low","assessor":"primary"}],"cwes":["CWE-367"],"updated_at":"2026-11-02T14:12:39.962615Z"}],"osv":[{"id":"CVE-2026-73829","title":"Non-atomic hash-credential dedup in mpp Tempo allows replay of a confirmed payment under a concurrent race","description":"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.","status":"published","published":"2026-08-19T17:19:43.696Z","modified":"2026-10-28T02:30:54.213797724Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium"}],"cwes":["CWE-367"],"updated_at":"2026-11-02T15:45:16.365946Z"},{"id":"EEF-CVE-2026-73829","title":"Non-atomic hash-credential dedup in mpp Tempo allows replay of a confirmed payment under a concurrent race","description":"## Summary\n\nTime-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.\n\n## Configurations\n\nThe 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.","status":"published","published":"2026-08-19T17:19:43.696Z","modified":"2026-09-08T05:45:02.680456301Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium"}],"cwes":["CWE-367"],"updated_at":"2026-11-02T15:46:33.520522Z"}]}}