CVE-2026-89186

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.

Affected Software

VendorProductVersion RangeStatus
ZenHivempp0.1.0 < 0.16.2affected
ZenHivempp2d4d1d94aae7790ae0623063961adbeef171fa71 < 2fd91a5ecbd0b0ad2a4ac202b79659e8126dbc0baffected

Weaknesses

  • CWE-524: CWE-524 Use of Cache Containing Sensitive Information

Workarounds

In the application mounted behind MPP.Plug, stop setting Cache-Control on paid routes so the library's 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.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References