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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"dateUpdated": "2026-09-16T14:49:54.770Z",
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"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.MPP.Methods.Tempo\u0027"
],
"packageName": "mpp",
"packageURL": "pkg:hex/mpp",
"product": "mpp",
"programFiles": [
"lib/mpp/methods/tempo.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.MPP.Methods.Tempo\u0027:verify/2"
}
],
"repo": "https://github.com/ZenHive/mpp",
"vendor": "ZenHive",
"versions": [
{
"lessThan": "0.16.2",
"status": "affected",
"version": "0.2.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.MPP.Methods.Tempo\u0027"
],
"packageName": "zenhive/mpp",
"packageURL": "pkg:github/zenhive/mpp",
"product": "mpp",
"programFiles": [
"lib/mpp/methods/tempo.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.MPP.Methods.Tempo\u0027:verify/2"
}
],
"repo": "https://github.com/ZenHive/mpp",
"vendor": "ZenHive",
"versions": [
{
"lessThan": "e12bd4a1cea2e97c2a01fc059c48e5594a7b4a43",
"status": "affected",
"version": "f8904666061fbab695874856d8fcd02c471dfe1b",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"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`."
}
],
"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."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*",
"versionEndExcluding": "0.16.2",
"versionStartIncluding": "0.2.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"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"
}
],
"dateAssigned": "2026-09-15T15:20:56.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"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."
}
],
"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."
}
],
"impacts": [
{
"capecId": "CAPEC-267",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"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."
}
],
"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."
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 6.3,
"baseSeverity": "MEDIUM",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"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",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "LOW",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-1289",
"description": "CWE-1289 Improper Validation of Unsafe Equivalence in Input",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-16T08:24:40.446Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"name": "GitHub Advisory",
"tags": [
"related",
"vendor-advisory"
],
"url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-8x7x-5j8g-8hcx"
},
{
"name": "EEF CNA record for CVE-2026-88255",
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-88255.html"
},
{
"name": "OSV record EEF-CVE-2026-88255",
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-88255"
},
{
"name": "Introducing commit f890466 in ZenHive/mpp",
"tags": [
"related"
],
"url": "https://github.com/ZenHive/mpp/commit/f8904666061fbab695874856d8fcd02c471dfe1b"
},
{
"name": "Fix commit e12bd4a in ZenHive/mpp",
"tags": [
"patch"
],
"url": "https://github.com/ZenHive/mpp/commit/e12bd4a1cea2e97c2a01fc059c48e5594a7b4a43"
}
],
"source": {
"discovery": "INTERNAL"
},
"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"
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-88255",
"datePublished": "2026-09-16T08:24:40.446Z",
"dateReserved": "2026-09-11T18:30:01.336Z",
"dateUpdated": "2026-09-16T14:49:57.782Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
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.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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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.