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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"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-89186\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-09-16T14:50:34.541725Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-09-16T14:50:40.806Z\"}}], \"cna\": {\"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\", \"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-204\", \"descriptions\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"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.\", \"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:L/VI:N/VA:N/SC:L/SI:N/SA:N\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"LOW\", \"vulnConfidentialityImpact\": \"LOW\", \"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.Plug\u0027\"], \"product\": \"mpp\", \"versions\": [{\"status\": \"affected\", \"version\": \"0.1.0\", \"lessThan\": \"0.16.2\", \"versionType\": \"semver\"}], \"packageURL\": \"pkg:hex/mpp\", \"packageName\": \"mpp\", \"programFiles\": [\"lib/mpp/plug.ex\"], \"collectionURL\": \"https://repo.hex.pm\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.MPP.Plug\u0027:call/2\"}]}, {\"cpes\": [\"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*\"], \"repo\": \"https://github.com/ZenHive/mpp\", \"vendor\": \"ZenHive\", \"modules\": [\"\u0027Elixir.MPP.Plug\u0027\"], \"product\": \"mpp\", \"versions\": [{\"status\": \"affected\", \"version\": \"2d4d1d94aae7790ae0623063961adbeef171fa71\", \"lessThan\": \"2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b\", \"versionType\": \"git\"}], \"packageURL\": \"pkg:github/zenhive/mpp\", \"packageName\": \"zenhive/mpp\", \"programFiles\": [\"lib/mpp/plug.ex\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.MPP.Plug\u0027:call/2\"}]}], \"references\": [{\"url\": \"https://github.com/ZenHive/mpp/security/advisories/GHSA-82qh-vrvm-gqvc\", \"name\": \"GitHub Advisory\", \"tags\": [\"related\", \"vendor-advisory\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-89186.html\", \"name\": \"EEF CNA record for CVE-2026-89186\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-89186\", \"name\": \"OSV record EEF-CVE-2026-89186\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/ZenHive/mpp/commit/2d4d1d94aae7790ae0623063961adbeef171fa71\", \"name\": \"Introducing commit 2d4d1d9 in ZenHive/mpp\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/ZenHive/mpp/commit/2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b\", \"name\": \"Fix commit 2fd91a5 in ZenHive/mpp\", \"tags\": [\"patch\"]}], \"workarounds\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"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.\", \"base64\": false}]}], \"dateAssigned\": \"2026-09-15T15:22:44.000Z\", \"descriptions\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"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.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-524\", \"description\": \"CWE-524 Use of Cache Containing Sensitive Information\"}]}], \"configurations\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"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.\", \"base64\": false}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"0.16.2\", \"versionStartIncluding\": \"0.1.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-09-16T08:24:15.058Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-89186\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-09-16T14:50:44.399Z\", \"dateReserved\": \"2026-09-11T19:00:02.549Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-09-16T08:24:15.058Z\", \"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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