Vulnerability-Lookup

GHSA-4H6W-PVRH-G28P

Vulnerability from github – Published: 2026-09-16 09:30 – Updated: 2026-09-16 09:30

Details

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

6.3 (Medium)


                  
                    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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-89186"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-524"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-16T09:17:07Z",
    "severity": "MODERATE"
  },
  "details": "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.",
  "id": "GHSA-4h6w-pvrh-g28p",
  "modified": "2026-09-16T09:30:29Z",
  "published": "2026-09-16T09:30:29Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-82qh-vrvm-gqvc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89186"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ZenHive/mpp/commit/2d4d1d94aae7790ae0623063961adbeef171fa71"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ZenHive/mpp/commit/2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b"
    },
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-89186.html"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-89186"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

CVE-2026-89186 (GCVE-0-2026-89186)

Vulnerability from cvelistv5 – Published: 2026-09-16 08:24 – Updated: 2026-09-16 08:24

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

6.3 (Medium)


                        
                          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

CWE

CWE-524 - Use of Cache Containing Sensitive Information

Assigner

EEF mitre root

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

2 products

Vendor	Product	Version
ZenHive	mpp	Affected: 0.1.0 , < 0.16.2 (semver) cpe:2.3:a:ZenHive:mpp::::::::
ZenHive	mpp	Affected: 2d4d1d94aae7790ae0623063961adbeef171fa71 , < 2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b (git) cpe:2.3:a:ZenHive:mpp::::::::

Credits

E.FU E.FU Jonatan Männchen / EEF

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JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "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"
            }
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        },
        {
          "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"
            }
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          "repo": "https://github.com/ZenHive/mpp",
          "vendor": "ZenHive",
          "versions": [
            {
              "lessThan": "2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b",
              "status": "affected",
              "version": "2d4d1d94aae7790ae0623063961adbeef171fa71",
              "versionType": "git"
            }
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        }
      ],
      "configurations": [
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              "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."
            }
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          "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."
        }
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      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*",
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          "type": "remediation developer",
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      ],
      "dateAssigned": "2026-09-15T15:22:44.000Z",
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            },
            {
              "base64": false,
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              "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": [
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                },
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                  "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."
            }
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        }
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      "metrics": [
        {
          "cvssV4_0": {
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            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
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            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
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            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
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            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
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            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "LOW",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
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      "providerMetadata": {
        "dateUpdated": "2026-09-16T08:24:15.058Z",
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        },
        {
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          "tags": [
            "related"
          ],
          "url": "https://osv.dev/vulnerability/EEF-CVE-2026-89186"
        },
        {
          "name": "Introducing commit 2d4d1d9 in ZenHive/mpp",
          "tags": [
            "related"
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          "url": "https://github.com/ZenHive/mpp/commit/2d4d1d94aae7790ae0623063961adbeef171fa71"
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          "tags": [
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      ],
      "source": {
        "discovery": "INTERNAL"
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      "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",
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              "type": "text/html",
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              "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."
        }
      ]
    }
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  "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": "2026-09-16T08:24:15.058Z",
    "state": "PUBLISHED"
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}

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.

Detection rules are retrieved from Rulezet.

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.

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.