CVE-2026-73829

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. The 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. This issue affects mpp: from 0.2.0 before 0.6.1.

CVSS v3 3.7 LOW

3.7^/10

CVSS v3 : LOW

Vector :

Exploitability : 2.2 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact LOW

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://cna.erlef.org/cves/CVE-2026-73829.html	Third Party Advisory
https://github.com/ZenHive/mpp/commit/46c5b0e1311da7d92190dc7d9ea89027a1d365e9	Patch
https://github.com/ZenHive/mpp/security/advisories/GHSA-w8j7-7qc3-5f24	Vendor Advisory
https://osv.dev/vulnerability/EEF-CVE-2026-73829	Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:zenhive:machine_payments_protocol:*:*:*:*:*:elixir:*:*

History

No history.

Information

Published : 2026-08-19 18:17

Updated : 2026-09-10 18:30

NVD link : CVE-2026-73829

Mitre link : CVE-2026-73829

CVE.ORG link : CVE-2026-73829

JSON object : View

Products Affected

zenhive

machine_payments_protocol

CWE

CWE-367

Time-of-check Time-of-use (TOCTOU) Race Condition

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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."}], "lastModified": "2026-09-10T18:30:09.270", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:zenhive:machine_payments_protocol:*:*:*:*:*:elixir:*:*", "vulnerable": true, "matchCriteriaId": "9C0F79DA-587D-4C5A-8376-08DB0FAF169A", "versionEndExcluding": "0.6.1", "versionStartIncluding": "0.2.0"}], "operator": "OR"}]}], "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}