CVE-2026-88255 (GCVE-0-2026-88255)
Vulnerability from cvelistv5
Published
2026-09-16 08:24
Modified
2026-09-16 14:49
Severity ?
VLAI Severity ?
EPSS score ?
CWE
- CWE-1289 - Improper Validation of Unsafe Equivalence in Input
Summary
Improper Validation of Unsafe Equivalence in Input in ZenHive mpp allows an unauthenticated remote client to pass the Tempo duplicate-submission gate twice with one signed transaction.
MPP.Methods.Tempo reserves the pre-broadcast dedup slot on the caller-supplied hex in reserve_hash_atomic/2, keyed through store_key/1 on tx.raw rather than on a canonical form of the transaction. The deserializer stores the caller's hex verbatim and accepts both recovery-id encodings, so one signed transaction submitted once with v=27 and once with v=0 yields two distinct reserve keys, and both pass the reserve and reach the broadcast path. The plug-level credential replay store is deliberately carved out for tempo in lib/mpp/replay.ex, leaving this reserve as the only gate, and the post-broadcast mark writes the canonical hash key that the raw-keyed reserve never reads.
What the duplicate submission yields depends on the node: a nonce-reuse rejection fails closed, while a node that answers with the canonical hash for an already-known transaction returns a second valid Payment-Receipt for a single on-chain payment.
This issue affects mpp: from 0.2.0 before 0.16.2.
References
Impacted products
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"value": "Reachable when `MPP.Methods.Tempo` broadcasts a `type=\"transaction\"` credential with a dedup store in place. From mpp 0.7.0 the dedup store is on by default (the app-started `MPP.Tempo.ConCacheStore`; opt out with `store: false`), so every default Tempo deployment from 0.7.0 before 0.16.2 is affected. Before 0.7.0 the default store was `nil`, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue; those versions are affected only where a `\"store\"` was configured explicitly in `method_config`."
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The plug-level credential replay store is deliberately carved out for \u003ccode\u003etempo\u003c/code\u003e in \u003ccode\u003elib/mpp/replay.ex\u003c/code\u003e, leaving this reserve as the only gate, and the post-broadcast mark writes the canonical hash key that the raw-keyed reserve never reads.\u003c/p\u003e\\n\u003cp\u003eWhat the duplicate submission yields depends on the node: a nonce-reuse rejection fails closed, while a node that answers with the canonical hash for an already-known transaction returns a second valid \u003ccode\u003ePayment-Receipt\u003c/code\u003e for a single on-chain payment.\u003c/p\u003e\\n\u003cp\u003eThis issue affects mpp: from 0.2.0 before 0.16.2.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Improper Validation of Unsafe Equivalence in Input in ZenHive mpp allows an unauthenticated remote client to pass the Tempo duplicate-submission gate twice with one signed transaction.\\n\\n`MPP.Methods.Tempo` reserves the pre-broadcast dedup slot on the caller-supplied hex in `reserve_hash_atomic/2`, keyed through `store_key/1` on `tx.raw` rather than on a canonical form of the transaction. The deserializer stores the caller\u0027s hex verbatim and accepts both recovery-id encodings, so one signed transaction submitted once with `v=27` and once with `v=0` yields two distinct reserve keys, and both pass the reserve and reach the broadcast path. The plug-level credential replay store is deliberately carved out for `tempo` in `lib/mpp/replay.ex`, leaving this reserve as the only gate, and the post-broadcast mark writes the canonical hash key that the raw-keyed reserve never reads.\\n\\nWhat the duplicate submission yields depends on the node: a nonce-reuse rejection fails closed, while a node that answers with the canonical hash for an already-known transaction returns a second valid `Payment-Receipt` for a single on-chain payment.\\n\\nThis issue affects mpp: from 0.2.0 before 0.16.2.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-1289\", \"description\": \"CWE-1289 Improper Validation of Unsafe Equivalence in Input\"}]}], \"configurations\": [{\"lang\": \"en\", \"value\": \"Reachable when MPP.Methods.Tempo broadcasts a type=\\\"transaction\\\" credential with a dedup store in place. From mpp 0.7.0 the dedup store is on by default (the app-started MPP.Tempo.ConCacheStore; opt out with store: false), so every default Tempo deployment from 0.7.0 before 0.16.2 is affected. Before 0.7.0 the default store was nil, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue; those versions are affected only where a \\\"store\\\" was configured explicitly in method_config.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eReachable when \u003ccode\u003eMPP.Methods.Tempo\u003c/code\u003e broadcasts a \u003ccode\u003etype=\\\"transaction\\\"\u003c/code\u003e credential with a dedup store in place. From mpp 0.7.0 the dedup store is on by default (the app-started \u003ccode\u003eMPP.Tempo.ConCacheStore\u003c/code\u003e; opt out with \u003ccode\u003estore: false\u003c/code\u003e), so every default Tempo deployment from 0.7.0 before 0.16.2 is affected. Before 0.7.0 the default store was \u003ccode\u003enil\u003c/code\u003e, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue; those versions are affected only where a \u003ccode\u003e\\\"store\\\"\u003c/code\u003e was configured explicitly in \u003ccode\u003emethod_config\u003c/code\u003e.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Reachable when `MPP.Methods.Tempo` broadcasts a `type=\\\"transaction\\\"` credential with a dedup store in place. From mpp 0.7.0 the dedup store is on by default (the app-started `MPP.Tempo.ConCacheStore`; opt out with `store: false`), so every default Tempo deployment from 0.7.0 before 0.16.2 is affected. Before 0.7.0 the default store was `nil`, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue; those versions are affected only where a `\\\"store\\\"` was configured explicitly in `method_config`.\", \"base64\": false}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"0.16.2\", \"versionStartIncluding\": \"0.2.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-09-16T08:24:40.446Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-88255\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-09-16T14:49:57.782Z\", \"dateReserved\": \"2026-09-11T18:30:01.336Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-09-16T08:24:40.446Z\", \"assignerShortName\": \"EEF\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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