{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0.2.0"
              },
              {
                "fixed": "0.16.2"
              }
            ],
            "source": [
              "DESCRIPTION",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "7ca7538f05959a98e0e5e63e4bd949b4f362cf8d"
            },
            {
              "fixed": "3b7e43abf60fa30c40985e4043965ec67791b4dc"
            },
            {
              "fixed": "e12bd4a1cea2e97c2a01fc059c48e5594a7b4a43"
            },
            {
              "fixed": "f8904666061fbab695874856d8fcd02c471dfe1b"
            }
          ],
          "repo": "https://github.com/zenhive/mpp",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-8x7x-5j8g-8hcx"
  ],
  "database_specific": {
    "cna_assigner": "EEF",
    "cwe_ids": [
      "CWE-1289"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/88xxx/CVE-2026-88255.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "f8904666061fbab695874856d8fcd02c471dfe1b"
          },
          {
            "fixed": "e12bd4a1cea2e97c2a01fc059c48e5594a7b4a43"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "Improper Validation of Unsafe Equivalence in Input in ZenHive mpp allows an unauthenticated remote client to pass the Tempo duplicate-submission gate twice with one signed transaction.\n\nMPP.Methods.Tempo reserves the pre-broadcast dedup slot on the caller-supplied hex in reserve_hash_atomic/2, keyed through store_key/1 on tx.raw rather than on a canonical form of the transaction. The deserializer stores the caller's hex verbatim and accepts both recovery-id encodings, so one signed transaction submitted once with v=27 and once with v=0 yields two distinct reserve keys, and both pass the reserve and reach the broadcast path. The plug-level credential replay store is deliberately carved out for tempo in lib/mpp/replay.ex, leaving this reserve as the only gate, and the post-broadcast mark writes the canonical hash key that the raw-keyed reserve never reads.\n\nWhat the duplicate submission yields depends on the node: a nonce-reuse rejection fails closed, while a node that answers with the canonical hash for an already-known transaction returns a second valid Payment-Receipt for a single on-chain payment.\n\nThis issue affects mpp: from 0.2.0 before 0.16.2.",
  "id": "CVE-2026-88255",
  "modified": "2026-09-18T03:30:19.522874747Z",
  "published": "2026-09-16T08:24:40.446Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-88255.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-88255"
    },
    {
      "type": "WEB",
      "url": "https://repo.hex.pm"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/88xxx/CVE-2026-88255.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/ZenHive/mpp/security/advisories/GHSA-8x7x-5j8g-8hcx"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-88255"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ZenHive/mpp/commit/e12bd4a1cea2e97c2a01fc059c48e5594a7b4a43"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ZenHive/mpp/commit/f8904666061fbab695874856d8fcd02c471dfe1b"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ZenHive/mpp"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "mpp Tempo keys its pre-broadcast dedup reserve on the caller-supplied transaction encoding, so a re-encoded signed transaction reserves a second slot"
}