CVE-2026-82751 (GCVE-0-2026-82751)
Vulnerability from cvelistv5 – Published: 2026-09-06 16:07 – Updated: 2026-09-08 18:24
VLAI
EPSS
VEX
Title
Unbounded key authorization in mpp Tempo fee-payer sponsorship inflates gas cost and sponsors access-key provisioning
Summary
Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.
When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.
This issue affects mpp: from 0.2.0 before 0.16.1.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-08 18:24 UTC
CWE
- CWE-1284 - Improper Validation of Specified Quantity in Input
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/ZenHive/mpp/security/advisorie… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-82751.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-82751 | related |
| https://github.com/ZenHive/mpp/commit/0482572b47e… | patch |
Impacted products
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"providerMetadata": {
"dateUpdated": "2026-09-08T18:24:11.950Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"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.FeePayerPolicy\u0027",
"\u0027Elixir.MPP.Methods.Tempo\u0027"
],
"packageName": "mpp",
"packageURL": "pkg:hex/mpp",
"product": "mpp",
"programFiles": [
"lib/mpp/methods/tempo/fee_payer_policy.ex",
"lib/mpp/methods/tempo.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.MPP.Methods.Tempo.FeePayerPolicy\u0027:measure/3"
},
{
"name": "\u0027Elixir.MPP.Methods.Tempo.FeePayerPolicy\u0027:validate/3"
},
{
"name": "\u0027Elixir.MPP.Methods.Tempo\u0027:verify/2"
}
],
"repo": "https://github.com/ZenHive/mpp",
"vendor": "ZenHive",
"versions": [
{
"lessThan": "0.16.1",
"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.FeePayerPolicy\u0027",
"\u0027Elixir.MPP.Methods.Tempo\u0027"
],
"packageName": "zenhive/mpp",
"packageURL": "pkg:github/zenhive/mpp",
"product": "mpp",
"programFiles": [
"lib/mpp/methods/tempo/fee_payer_policy.ex",
"lib/mpp/methods/tempo.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.MPP.Methods.Tempo.FeePayerPolicy\u0027:measure/3"
},
{
"name": "\u0027Elixir.MPP.Methods.Tempo.FeePayerPolicy\u0027:validate/3"
},
{
"name": "\u0027Elixir.MPP.Methods.Tempo\u0027:verify/2"
}
],
"repo": "https://github.com/ZenHive/mpp",
"vendor": "ZenHive",
"versions": [
{
"lessThan": "0482572b47e1ffe1537ab80ab613d47b92833c2d",
"status": "affected",
"version": "d29d54e507918db00a5b65d90136b73166c017d7",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eOnly deployments that enable Tempo server-side fee sponsorship are affected, through \u003ccode\u003e\"fee_payer\" =\u0026gt; true\u003c/code\u003e in \u003ccode\u003emethod_config\u003c/code\u003e with either local co-signing (\u003ccode\u003efee_payer_private_key\u003c/code\u003e) or hosted sponsorship (\u003ccode\u003efee_payer_url\u003c/code\u003e). Sponsorship is disabled by default.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Only deployments that enable Tempo server-side fee sponsorship are affected, through `\"fee_payer\" =\u003e true` in `method_config` with either local co-signing (`fee_payer_private_key`) or hosted sponsorship (`fee_payer_url`). Sponsorship is disabled by default."
}
],
"value": "Only deployments that enable Tempo server-side fee sponsorship are affected, through \"fee_payer\" =\u003e true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*",
"versionEndExcluding": "0.16.1",
"versionStartIncluding": "0.2.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
],
"operator": "AND"
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Kian Kai Ang"
},
{
"lang": "en",
"type": "reporter",
"value": "Kian Kai Ang"
},
{
"lang": "en",
"type": "remediation developer",
"value": "E.FU"
},
{
"lang": "en",
"type": "coordinator",
"value": "Jonatan M\u00e4nnchen / EEF"
}
],
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eImproper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer\u0027s gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client\u0027s own account.\u003c/p\u003e\n\u003cp\u003eWhen the server sponsors Tempo payments, \u003ccode\u003eMPP.Methods.Tempo.FeePayerPolicy.measure/3\u003c/code\u003e in \u003ccode\u003elib/mpp/methods/tempo/fee_payer_policy.ex\u003c/code\u003e bounds the gas fields, the fee budget, the validity window and the access list of the client-signed \u003ccode\u003e0x76\u003c/code\u003e envelope, but does not check whether the envelope carries the optional \u003ccode\u003ekey_authorization\u003c/code\u003e field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the \u003ccode\u003egas_limit\u003c/code\u003e ceiling. At the reporter\u0027s default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.\u003c/p\u003e\n\u003cp\u003eThis issue affects mpp: from 0.2.0 before 0.16.1.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer\u0027s gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client\u0027s own account.\n\nWhen the server sponsors Tempo payments, `MPP.Methods.Tempo.FeePayerPolicy.measure/3` in `lib/mpp/methods/tempo/fee_payer_policy.ex` bounds the gas fields, the fee budget, the validity window and the access list of the client-signed `0x76` envelope, but does not check whether the envelope carries the optional `key_authorization` field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the `gas_limit` ceiling. At the reporter\u0027s default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.\n\nThis issue affects mpp: from 0.2.0 before 0.16.1."
}
],
"value": "Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer\u0027s gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client\u0027s own account.\n\nWhen the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter\u0027s default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.\n\nThis issue affects mpp: from 0.2.0 before 0.16.1."
}
],
"impacts": [
{
"capecId": "CAPEC-130",
"descriptions": [
{
"lang": "en",
"value": "CAPEC-130 Excessive Allocation"
}
]
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 8.3,
"baseSeverity": "HIGH",
"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:H/VA:L/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "LOW",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-1284",
"description": "CWE-1284 Improper Validation of Specified Quantity in Input",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-06T16:07:26.407Z",
"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"shortName": "EEF"
},
"references": [
{
"tags": [
"vendor-advisory",
"related"
],
"url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-rpwj-vrf7-4x36"
},
{
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-82751.html"
},
{
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-82751"
},
{
"tags": [
"patch"
],
"url": "https://github.com/ZenHive/mpp/commit/0482572b47e1ffe1537ab80ab613d47b92833c2d"
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Unbounded key authorization in mpp Tempo fee-payer sponsorship inflates gas cost and sponsors access-key provisioning",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eDisable Tempo fee sponsorship by leaving \u003ccode\u003e\"fee_payer\"\u003c/code\u003e at its default of \u003ccode\u003efalse\u003c/code\u003e and setting no \u003ccode\u003efee_payer_url\u003c/code\u003e, so the client pays its own gas. Where sponsorship must stay enabled, lower the \u003ccode\u003emax_gas\u003c/code\u003e override in \u003ccode\u003efee_payer_policy\u003c/code\u003e to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Disable Tempo fee sponsorship by leaving `\"fee_payer\"` at its default of `false` and setting no `fee_payer_url`, so the client pays its own gas. Where sponsorship must stay enabled, lower the `max_gas` override in `fee_payer_policy` to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it."
}
],
"value": "Disable Tempo fee sponsorship by leaving \"fee_payer\" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it."
}
]
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-82751",
"datePublished": "2026-09-06T16:07:26.407Z",
"dateReserved": "2026-08-31T01:00:09.775Z",
"dateUpdated": "2026-09-08T18:24:19.598Z",
"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.