CVE-2026-89420

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

• https://cna.erlef.org/cves/CVE-2026-89420.html 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
• https://github.com/ZenHive/mpp/commit/7270edc1dcfb58250cc5ee812876609206564165 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
• https://github.com/ZenHive/mpp/commit/82df569c898be1137189e3648e1edb4af6363651 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
• https://github.com/ZenHive/mpp/security/advisories/GHSA-8c63-r789-xrrf 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
• https://github.com/ZenHive/mpp/security/advisories/GHSA-8c63-r789-xrrf 134c704f-9b21-4f2e-91b3-4a467353bcc0
• https://osv.dev/vulnerability/EEF-CVE-2026-89420 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

The full cvelistV5 record. Download as CVE-2026-89420.json.

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-89420",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-22T12:03:58.968313Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-22T12:04:43.291Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-8c63-r789-xrrf"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "'Elixir.MPP.Session.Actions'"
          ],
          "packageName": "mpp",
          "packageURL": "pkg:hex/mpp",
          "product": "mpp",
          "programFiles": [
            "lib/mpp/session/actions.ex"
          ],
          "programRoutines": [
            {
              "name": "'Elixir.MPP.Session.Actions':dispatch/2"
            },
            {
              "name": "'Elixir.MPP.Session.Actions':handle/2"
            }
          ],
          "repo": "https://github.com/ZenHive/mpp",
          "vendor": "ZenHive",
          "versions": [
            {
              "lessThan": "0.16.2",
              "status": "affected",
              "version": "0.14.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "'Elixir.MPP.Session.Actions'"
          ],
          "packageName": "zenhive/mpp",
          "packageURL": "pkg:github/zenhive/mpp",
          "product": "mpp",
          "programFiles": [
            "lib/mpp/session/actions.ex"
          ],
          "programRoutines": [
            {
              "name": "'Elixir.MPP.Session.Actions':dispatch/2"
            },
            {
              "name": "'Elixir.MPP.Session.Actions':handle/2"
            }
          ],
          "repo": "https://github.com/ZenHive/mpp",
          "vendor": "ZenHive",
          "versions": [
            {
              "lessThan": "7270edc1dcfb58250cc5ee812876609206564165",
              "status": "affected",
              "version": "82df569c898be1137189e3648e1edb4af6363651",
              "versionType": "git"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:ZenHive:mpp:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "0.16.2",
                  "versionStartIncluding": "0.14.0",
                  "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": "2026-09-15T15:23:05.000Z",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "<p>Improper Validation of Specified Quantity in Input in ZenHive mpp allows a client holding an open payment channel to obtain paid resources without being charged.</p>\n<p><code>MPP.Session.Actions.accept_voucher/3</code> in <code>lib/mpp/session/actions.ex</code> treats a voucher whose <code>cumulativeAmount</code> equals the channel's already-accepted cumulative amount as an idempotent success, returning the channel unchanged without calling <code>maybe_spend/2</code>. The credential verifies, the protected resource is served, and <code>spent</code> and <code>units</code> stay where they were. Because the server issues a fresh challenge per request and the credential replay store keys on challenge id and payload, the same signed voucher can be re-presented under every new challenge, so one paid voucher yields an unbounded number of paid units. The path is reachable from any method built on <code>MPP.Session.Method</code> through the Plug, MCP, JSON-RPC and WebSocket transports.</p>\n<p>This issue affects mpp: from 0.14.0 before 0.16.2.</p>"
            },
            {
              "base64": false,
              "type": "text/markdown",
              "value": "Improper Validation of Specified Quantity in Input in ZenHive mpp allows a client holding an open payment channel to obtain paid resources without being charged.\n\n`MPP.Session.Actions.accept_voucher/3` in `lib/mpp/session/actions.ex` treats a voucher whose `cumulativeAmount` equals the channel's already-accepted cumulative amount as an idempotent success, returning the channel unchanged without calling `maybe_spend/2`. The credential verifies, the protected resource is served, and `spent` and `units` stay where they were. Because the server issues a fresh challenge per request and the credential replay store keys on challenge id and payload, the same signed voucher can be re-presented under every new challenge, so one paid voucher yields an unbounded number of paid units. The path is reachable from any method built on `MPP.Session.Method` through the Plug, MCP, JSON-RPC and WebSocket transports.\n\nThis issue affects mpp: from 0.14.0 before 0.16.2."
            }
          ],
          "value": "Improper Validation of Specified Quantity in Input in ZenHive mpp allows a client holding an open payment channel to obtain paid resources without being charged.\n\nMPP.Session.Actions.accept_voucher/3 in lib/mpp/session/actions.ex treats a voucher whose cumulativeAmount equals the channel's already-accepted cumulative amount as an idempotent success, returning the channel unchanged without calling maybe_spend/2. The credential verifies, the protected resource is served, and spent and units stay where they were. Because the server issues a fresh challenge per request and the credential replay store keys on challenge id and payload, the same signed voucher can be re-presented under every new challenge, so one paid voucher yields an unbounded number of paid units. The path is reachable from any method built on MPP.Session.Method through the Plug, MCP, JSON-RPC and WebSocket transports.\n\nThis issue affects mpp: from 0.14.0 before 0.16.2."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-212",
          "descriptions": [
            {
              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "<p>A client that has opened and funded a payment channel once can re-present the same signed voucher indefinitely and receive paid resources without any further charge. Operators running mpp as paid-API middleware lose revenue in proportion to how much the client consumes, with nothing in the channel state recording the usage.</p>"
                },
                {
                  "base64": false,
                  "type": "text/markdown",
                  "value": "A client that has opened and funded a payment channel once can re-present the same signed voucher indefinitely and receive paid resources without any further charge. Operators running mpp as paid-API middleware lose revenue in proportion to how much the client consumes, with nothing in the channel state recording the usage."
                }
              ],
              "value": "A client that has opened and funded a payment channel once can re-present the same signed voucher indefinitely and receive paid resources without any further charge. Operators running mpp as paid-API middleware lose revenue in proportion to how much the client consumes, with nothing in the channel state recording the usage."
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1284",
              "description": "CWE-1284 Improper Validation of Specified Quantity in Input",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-22T11:16:29.573Z",
        "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-8c63-r789-xrrf"
        },
        {
          "name": "EEF CNA record for CVE-2026-89420",
          "tags": [
            "related"
          ],
          "url": "https://cna.erlef.org/cves/CVE-2026-89420.html"
        },
        {
          "name": "OSV record EEF-CVE-2026-89420",
          "tags": [
            "related"
          ],
          "url": "https://osv.dev/vulnerability/EEF-CVE-2026-89420"
        },
        {
          "name": "Introducing commit 82df569 in ZenHive/mpp",
          "tags": [
            "related"
          ],
          "url": "https://github.com/ZenHive/mpp/commit/82df569c898be1137189e3648e1edb4af6363651"
        },
        {
          "name": "Fix commit 7270edc in ZenHive/mpp",
          "tags": [
            "patch"
          ],
          "url": "https://github.com/ZenHive/mpp/commit/7270edc1dcfb58250cc5ee812876609206564165"
        }
      ],
      "source": {
        "discovery": "INTERNAL"
      },
      "title": "Session voucher adding no new funds is accepted without a charge in mpp, serving paid resources for free"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
    "assignerShortName": "EEF",
    "cveId": "CVE-2026-89420",
    "datePublished": "2026-09-22T11:16:29.573Z",
    "dateReserved": "2026-09-11T19:00:02.531Z",
    "dateUpdated": "2026-09-22T12:04:43.291Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}