CVE-2026-88255 (GCVE-0-2026-88255)
Vulnerability from cvelistv5 – Published: 2026-09-16 08:24 – Updated: 2026-09-16 14:49
VLAI
EPSS
VEX
Title
mpp Tempo keys its pre-broadcast dedup reserve on the caller-supplied transaction encoding, so a re-encoded signed transaction reserves a second slot
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.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-16 14:49 UTC
CWE
- CWE-1289 - Improper Validation of Unsafe Equivalence in Input
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://github.com/ZenHive/mpp/security/advisorie… | relatedvendor-advisory |
| https://cna.erlef.org/cves/CVE-2026-88255.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-88255 | related |
| https://github.com/ZenHive/mpp/commit/f8904666061… | related |
| https://github.com/ZenHive/mpp/commit/e12bd4a1cea… | patch |
Impacted products
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"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-88255\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-09-16T14:49:50.266563Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-09-16T14:49:54.770Z\"}}], \"cna\": {\"title\": \"mpp Tempo keys its pre-broadcast dedup reserve on the caller-supplied transaction encoding, so a re-encoded signed transaction reserves a second slot\", \"source\": {\"discovery\": \"INTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"E.FU\"}, {\"lang\": \"en\", \"type\": \"remediation developer\", \"value\": \"E.FU\"}, {\"lang\": \"en\", \"type\": \"coordinator\", \"value\": \"Jonatan M\\u00e4nnchen / EEF\"}], \"impacts\": [{\"capecId\": \"CAPEC-267\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"A client re-encodes the recovery id of a transaction it has already submitted and presents it again. The duplicate passes the only duplicate-submission gate the Tempo method has, and against a node that answers with the canonical hash for an already-known transaction the client is issued a second Payment-Receipt for one on-chain payment.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eA client re-encodes the recovery id of a transaction it has already submitted and presents it again. The duplicate passes the only duplicate-submission gate the Tempo method has, and against a node that answers with the canonical hash for an already-known transaction the client is issued a second \u003ccode\u003ePayment-Receipt\u003c/code\u003e for one on-chain payment.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"A client re-encodes the recovery id of a transaction it has already submitted and presents it again. The duplicate passes the only duplicate-submission gate the Tempo method has, and against a node that answers with the canonical hash for an already-known transaction the client is issued a second `Payment-Receipt` for one on-chain payment.\", \"base64\": false}]}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 6.3, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"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\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"LOW\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/ZenHive/mpp\", \"vendor\": \"ZenHive\", \"modules\": [\"\u0027Elixir.MPP.Methods.Tempo\u0027\"], \"product\": \"mpp\", \"versions\": [{\"status\": \"affected\", \"version\": \"0.2.0\", \"lessThan\": \"0.16.2\", \"versionType\": \"semver\"}], \"packageURL\": \"pkg:hex/mpp\", \"packageName\": \"mpp\", \"programFiles\": [\"lib/mpp/methods/tempo.ex\"], \"collectionURL\": \"https://repo.hex.pm\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.MPP.Methods.Tempo\u0027:verify/2\"}]}, {\"cpes\": [\"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/ZenHive/mpp\", \"vendor\": \"ZenHive\", \"modules\": [\"\u0027Elixir.MPP.Methods.Tempo\u0027\"], \"product\": \"mpp\", \"versions\": [{\"status\": \"affected\", \"version\": \"f8904666061fbab695874856d8fcd02c471dfe1b\", \"lessThan\": \"e12bd4a1cea2e97c2a01fc059c48e5594a7b4a43\", \"versionType\": \"git\"}], \"packageURL\": \"pkg:github/zenhive/mpp\", \"packageName\": \"zenhive/mpp\", \"programFiles\": [\"lib/mpp/methods/tempo.ex\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.MPP.Methods.Tempo\u0027:verify/2\"}]}], \"references\": [{\"url\": \"https://github.com/ZenHive/mpp/security/advisories/GHSA-8x7x-5j8g-8hcx\", \"name\": \"GitHub Advisory\", \"tags\": [\"related\", \"vendor-advisory\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-88255.html\", \"name\": \"EEF CNA record for CVE-2026-88255\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-88255\", \"name\": \"OSV record EEF-CVE-2026-88255\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/ZenHive/mpp/commit/f8904666061fbab695874856d8fcd02c471dfe1b\", \"name\": \"Introducing commit f890466 in ZenHive/mpp\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/ZenHive/mpp/commit/e12bd4a1cea2e97c2a01fc059c48e5594a7b4a43\", \"name\": \"Fix commit e12bd4a in ZenHive/mpp\", \"tags\": [\"patch\"]}], \"dateAssigned\": \"2026-09-15T15:20:56.000Z\", \"descriptions\": [{\"lang\": \"en\", \"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\\nMPP.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.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eImproper 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.\u003c/p\u003e\\n\u003cp\u003e\u003ccode\u003eMPP.Methods.Tempo\u003c/code\u003e reserves the pre-broadcast dedup slot on the caller-supplied hex in \u003ccode\u003ereserve_hash_atomic/2\u003c/code\u003e, keyed through \u003ccode\u003estore_key/1\u003c/code\u003e on \u003ccode\u003etx.raw\u003c/code\u003e 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 \u003ccode\u003ev=27\u003c/code\u003e and once with \u003ccode\u003ev=0\u003c/code\u003e 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 \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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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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