---
id: CVE-2026-89186
title: >-
  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-contr…
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-contr…
severity: medium
cvss: 6.3
cvssVector: '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
vendor: ZenHive
product: mpp
affected:
  - mpp >= 0.1.0 < 0.16.2
  - >-
    zenhive/mpp >= 2d4d1d94aae7790ae0623063961adbeef171fa71 <
    2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b
published: '2026-09-16'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T20:38:33.883'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89186'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-89186.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/ZenHive/mpp/commit/2d4d1d94aae7790ae0623063961adbeef171fa71
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/ZenHive/mpp/commit/2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0b
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://github.com/ZenHive/mpp/security/advisories/GHSA-82qh-vrvm-gqvc'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-89186'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-16T14:50:34.541725Z'
cvssSource: cna
ingestedAt: '2026-09-16T08:52:29.600Z'
epss: 0.00524
epssPercentile: 0.41914
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.