CVE-2026-73829
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. 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.
INFO
Published Date :
Aug. 19, 2026, 6:17 p.m.
Last Modified :
Aug. 19, 2026, 7:17 p.m.
Remotely Exploit :
Yes !
Source :
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | ||||
| CVSS 4.0 | MEDIUM | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db |
Solution
- Update ZenHive mpp to version 0.6.1 or later.
- Ensure atomic check_and_mark is used for the hash path.
- Configure a dedup store if replay protection is needed.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-73829.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-73829 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-73829
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-73829 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-73829 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 19, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-73829', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-19T18:55:14.304500Z'} -
New CVE Received by 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Aug. 19, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/ZenHive/mpp', 'vendor': 'ZenHive', 'modules': ["'Elixir.MPP.Methods.Tempo'"], 'product': 'mpp', 'versions': [{'status': 'affected', 'version': '0.2.0', 'lessThan': '0.6.1', 'versionType': 'semver'}], 'packageURL': 'pkg:hex/mpp', 'packageName': 'mpp', 'programFiles': ['lib/mpp/methods/tempo.ex'], 'collectionURL': 'https://repo.hex.pm', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.MPP.Methods.Tempo':verify/2"}]}, {'cpes': ['cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*'], 'repo': 'https://github.com/ZenHive/mpp', 'vendor': 'ZenHive', 'modules': ["'Elixir.MPP.Methods.Tempo'"], 'product': 'mpp', 'versions': [{'status': 'affected', 'version': 'f8904666061fbab695874856d8fcd02c471dfe1b', 'lessThan': '46c5b0e1311da7d92190dc7d9ea89027a1d365e9', 'versionType': 'git'}], 'packageURL': 'pkg:github/zenhive/mpp', 'packageName': 'zenhive/mpp', 'programFiles': ['lib/mpp/methods/tempo.ex'], 'collectionURL': 'https://github.com', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': "'Elixir.MPP.Methods.Tempo':verify/2"}]}] Added 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. 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. Added CVSS V4.0 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 Added CWE CWE-367 Added Reference https://cna.erlef.org/cves/CVE-2026-73829.html Added Reference https://github.com/ZenHive/mpp/commit/46c5b0e1311da7d92190dc7d9ea89027a1d365e9 Added Reference https://github.com/ZenHive/mpp/security/advisories/GHSA-w8j7-7qc3-5f24 Added Reference https://osv.dev/vulnerability/EEF-CVE-2026-73829