Answer in brief
CVE-2026-73829 records a Medium severity (CVSS 6.3) vulnerability in Non-atomic hash-credential dedup in mpp Tempo allows replay of a confirmed payment under a concurrent race. The current sources do not mark it as known exploited. The current feed maps ZenHive/mpp (generic), ZenHive/mpp (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 6.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps ZenHive/mpp (generic), ZenHive/mpp (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:zenhive:machine_payments_protocol:*:*:*:*:*:elixir:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| ZenHive/mppgeneric | >=0.2.0 <0.6.1 | 0.6.1 |
| ZenHive/mppgeneric | >=f8904666061fbab695874856d8fcd02c471dfe1b <46c5b0e1311da7d92190dc7d9ea89027a1d365e9 | 46c5b0e1311da7d92190dc7d9ea89027a1d365e9 |
Published upstream
Aug 19, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 19, 2026
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.
Quoted source text, attributed separately from HOL analysis.