CVE-2026-89186 (GCVE-0-2026-89186)
Vulnerability from cvelistv5 – Published: 2026-09-16 08:24 – Updated: 2026-09-16 14:50
VLAI
EPSS
VEX
Title
mpp writes Payment-Receipt and Cache-Control before the wrapped application runs, letting a consumer's own Cache-Control expose paid responses to shared caches
Summary
Use of Cache Containing Sensitive Information in ZenHive mpp allows a shared HTTP cache to store a paid response and serve it to clients that never paid.
MPP.Plug.verify_credential in lib/mpp/plug.ex sets payment-receipt and cache-control: private on the connection before the wrapped application runs, and registers no register_before_send/2 callback. Plug.Conn.put_resp_header/3 replaces an existing header, so a mounting application that sets its own cache-control on the paid resource (for example public, max-age=3600) silently overrides the private the library relies on, and a CDN or reverse proxy can then store the paid 200 together with its Payment-Receipt and serve both to unpaid clients. The library-level guarantee is therefore defeatable by the application it protects. For the same reason a downstream non-2xx response still carried Payment-Receipt, issuing a receipt for a response that delivered no resource.
This issue affects mpp: from 0.1.0 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 14:50 UTC
CWE
- CWE-524 - Use of Cache Containing Sensitive Information
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://github.com/ZenHive/mpp/security/advisorie… | relatedvendor-advisory |
| https://cna.erlef.org/cves/CVE-2026-89186.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-89186 | related |
| https://github.com/ZenHive/mpp/commit/2d4d1d94aae… | related |
| https://github.com/ZenHive/mpp/commit/2fd91a5ecbd… | patch |
Impacted products
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"modules": [
"\u0027Elixir.MPP.Plug\u0027"
],
"packageName": "mpp",
"packageURL": "pkg:hex/mpp",
"product": "mpp",
"programFiles": [
"lib/mpp/plug.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.MPP.Plug\u0027:call/2"
}
],
"repo": "https://github.com/ZenHive/mpp",
"vendor": "ZenHive",
"versions": [
{
"lessThan": "0.16.2",
"status": "affected",
"version": "0.1.0",
"versionType": "semver"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.MPP.Plug\u0027"
],
"packageName": "zenhive/mpp",
"packageURL": "pkg:github/zenhive/mpp",
"product": "mpp",
"programFiles": [
"lib/mpp/plug.ex"
],
"programRoutines": [
{
"name": "\u0027Elixir.MPP.Plug\u0027:call/2"
}
],
"repo": "https://github.com/ZenHive/mpp",
"vendor": "ZenHive",
"versions": [
{
"lessThan": "2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b",
"status": "affected",
"version": "2d4d1d94aae7790ae0623063961adbeef171fa71",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eReachable only where the application mounted behind \u003ccode\u003eMPP.Plug\u003c/code\u003e sets its own \u003ccode\u003eCache-Control\u003c/code\u003e on the paid resource, overriding the \u003ccode\u003eprivate\u003c/code\u003e the library wrote, and a shared HTTP cache (CDN or reverse proxy) sits in front of that route. An application that sets no \u003ccode\u003eCache-Control\u003c/code\u003e of its own keeps the library\u0027s \u003ccode\u003eprivate\u003c/code\u003e and is not affected.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Reachable only where the application mounted behind `MPP.Plug` sets its own `Cache-Control` on the paid resource, overriding the `private` the library wrote, and a shared HTTP cache (CDN or reverse proxy) sits in front of that route. An application that sets no `Cache-Control` of its own keeps the library\u0027s `private` and is not affected."
}
],
"value": "Reachable only where the application mounted behind MPP.Plug sets its own Cache-Control on the paid resource, overriding the private the library wrote, and a shared HTTP cache (CDN or reverse proxy) sits in front of that route. An application that sets no Cache-Control of its own keeps the library\u0027s private and is not affected."
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*",
"versionEndExcluding": "0.16.2",
"versionStartIncluding": "0.1.0",
"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": "2026-09-15T15:22:44.000Z",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eUse of Cache Containing Sensitive Information in ZenHive mpp allows a shared HTTP cache to store a paid response and serve it to clients that never paid.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eMPP.Plug.verify_credential\u003c/code\u003e in \u003ccode\u003elib/mpp/plug.ex\u003c/code\u003e sets \u003ccode\u003epayment-receipt\u003c/code\u003e and \u003ccode\u003ecache-control: private\u003c/code\u003e on the connection before the wrapped application runs, and registers no \u003ccode\u003eregister_before_send/2\u003c/code\u003e callback. \u003ccode\u003ePlug.Conn.put_resp_header/3\u003c/code\u003e replaces an existing header, so a mounting application that sets its own \u003ccode\u003ecache-control\u003c/code\u003e on the paid resource (for example \u003ccode\u003epublic, max-age=3600\u003c/code\u003e) silently overrides the \u003ccode\u003eprivate\u003c/code\u003e the library relies on, and a CDN or reverse proxy can then store the paid 200 together with its \u003ccode\u003ePayment-Receipt\u003c/code\u003e and serve both to unpaid clients. The library-level guarantee is therefore defeatable by the application it protects. For the same reason a downstream non-2xx response still carried \u003ccode\u003ePayment-Receipt\u003c/code\u003e, issuing a receipt for a response that delivered no resource.\u003c/p\u003e\n\u003cp\u003eThis issue affects mpp: from 0.1.0 before 0.16.2.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "Use of Cache Containing Sensitive Information in ZenHive mpp allows a shared HTTP cache to store a paid response and serve it to clients that never paid.\n\n`MPP.Plug.verify_credential` in `lib/mpp/plug.ex` sets `payment-receipt` and `cache-control: private` on the connection before the wrapped application runs, and registers no `register_before_send/2` callback. `Plug.Conn.put_resp_header/3` replaces an existing header, so a mounting application that sets its own `cache-control` on the paid resource (for example `public, max-age=3600`) silently overrides the `private` the library relies on, and a CDN or reverse proxy can then store the paid 200 together with its `Payment-Receipt` and serve both to unpaid clients. The library-level guarantee is therefore defeatable by the application it protects. For the same reason a downstream non-2xx response still carried `Payment-Receipt`, issuing a receipt for a response that delivered no resource.\n\nThis issue affects mpp: from 0.1.0 before 0.16.2."
}
],
"value": "Use of Cache Containing Sensitive Information in ZenHive mpp allows a shared HTTP cache to store a paid response and serve it to clients that never paid.\n\nMPP.Plug.verify_credential in lib/mpp/plug.ex sets payment-receipt and cache-control: private on the connection before the wrapped application runs, and registers no register_before_send/2 callback. Plug.Conn.put_resp_header/3 replaces an existing header, so a mounting application that sets its own cache-control on the paid resource (for example public, max-age=3600) silently overrides the private the library relies on, and a CDN or reverse proxy can then store the paid 200 together with its Payment-Receipt and serve both to unpaid clients. The library-level guarantee is therefore defeatable by the application it protects. For the same reason a downstream non-2xx response still carried Payment-Receipt, issuing a receipt for a response that delivered no resource.\n\nThis issue affects mpp: from 0.1.0 before 0.16.2."
}
],
"impacts": [
{
"capecId": "CAPEC-204",
"descriptions": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eAn unpaid client requesting the same URL through the shared cache receives the cached paid response, including the \u003ccode\u003ePayment-Receipt\u003c/code\u003e header issued to the paying client. Operators lose the revenue for every cache hit, and the receipt identifying a paid transaction is disclosed to third parties.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "An unpaid client requesting the same URL through the shared cache receives the cached paid response, including the `Payment-Receipt` header issued to the paying client. Operators lose the revenue for every cache hit, and the receipt identifying a paid transaction is disclosed to third parties."
}
],
"value": "An unpaid client requesting the same URL through the shared cache receives the cached paid response, including the Payment-Receipt header issued to the paying client. Operators lose the revenue for every cache hit, and the receipt identifying a paid transaction is disclosed to third parties."
}
]
}
],
"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": "LOW",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "LOW",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-524",
"description": "CWE-524 Use of Cache Containing Sensitive Information",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-16T08:24:15.058Z",
"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-82qh-vrvm-gqvc"
},
{
"name": "EEF CNA record for CVE-2026-89186",
"tags": [
"related"
],
"url": "https://cna.erlef.org/cves/CVE-2026-89186.html"
},
{
"name": "OSV record EEF-CVE-2026-89186",
"tags": [
"related"
],
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-89186"
},
{
"name": "Introducing commit 2d4d1d9 in ZenHive/mpp",
"tags": [
"related"
],
"url": "https://github.com/ZenHive/mpp/commit/2d4d1d94aae7790ae0623063961adbeef171fa71"
},
{
"name": "Fix commit 2fd91a5 in ZenHive/mpp",
"tags": [
"patch"
],
"url": "https://github.com/ZenHive/mpp/commit/2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b"
}
],
"source": {
"discovery": "INTERNAL"
},
"title": "mpp writes Payment-Receipt and Cache-Control before the wrapped application runs, letting a consumer\u0027s own Cache-Control expose paid responses to shared caches",
"workarounds": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"value": "\u003cp\u003eIn the application mounted behind \u003ccode\u003eMPP.Plug\u003c/code\u003e, stop setting \u003ccode\u003eCache-Control\u003c/code\u003e on paid routes so the library\u0027s \u003ccode\u003eprivate\u003c/code\u003e survives to the response, or set a directive that is itself safe for a shared cache (\u003ccode\u003eprivate\u003c/code\u003e, or \u003ccode\u003eno-store\u003c/code\u003e). Where the application must set its own caching policy, configure the CDN or reverse proxy not to cache responses carrying a \u003ccode\u003ePayment-Receipt\u003c/code\u003e header.\u003c/p\u003e"
},
{
"base64": false,
"type": "text/markdown",
"value": "In the application mounted behind `MPP.Plug`, stop setting `Cache-Control` on paid routes so the library\u0027s `private` survives to the response, or set a directive that is itself safe for a shared cache (`private`, or `no-store`). Where the application must set its own caching policy, configure the CDN or reverse proxy not to cache responses carrying a `Payment-Receipt` header."
}
],
"value": "In the application mounted behind MPP.Plug, stop setting Cache-Control on paid routes so the library\u0027s private survives to the response, or set a directive that is itself safe for a shared cache (private, or no-store). Where the application must set its own caching policy, configure the CDN or reverse proxy not to cache responses carrying a Payment-Receipt header."
}
]
}
},
"cveMetadata": {
"assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"assignerShortName": "EEF",
"cveId": "CVE-2026-89186",
"datePublished": "2026-09-16T08:24:15.058Z",
"dateReserved": "2026-09-11T19:00:02.549Z",
"dateUpdated": "2026-09-16T14:50:44.399Z",
"state": "PUBLISHED"
},
"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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