Poseidon V1 variable-length input collision via implicit zero-padding

{
  "id": "ac2db6a7f8557820ad664cfe5fa3d6f21e318045fd38c3772957b399b936371b",
  "url": "https://osv.dev/vulnerability/CVE-2026-32129",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Poseidon V1 variable-length input collision via implicit zero-padding",
    "summary": "soroban-poseidon provides Poseidon and Poseidon2 cryptographic hash functions for Soroban smart contracts. Poseidon V1 (PoseidonSponge) accepts variable-length inputs without injective padding. When a caller provides fewer inputs than the sponge rate (inputs.len() < T - 1), unused rate positions are implicitly zero-filled. This allows trivial hash collisions: for any input vector [m1, ..., mk] hashed with a sponge of rate > k, hash([m1, ..., mk]) equals hash([m1, ..., mk, 0]) because both produce identical pre-permutation states. This affects any use of PoseidonSponge or poseidon_hash where the number of inputs is less than T - 1 (e.g., hashing 1 input with T=3). Poseidon2 (Poseidon2Sponge) is not affected.",
    "evidence": "osv:CVE-2026-32129",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-32129",
      "aliases": [
        "CVE-2026-32129",
        "GHSA-g2p6-hh5v-7hfm"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/stellar/rs-soroban-poseidon",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "024fc7a7a4fbad6f09102879fe15b3daf87a016c"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "25.0.1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "024fc7a7a4fbad6f09102879fe15b3daf87a016c"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v25.0.1"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v25.0.0",
            "v25.0.0-rc.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-32129.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:35.940141488Z",
      "provider": "osv",
      "references": [
        "https://github.com/stellar/rs-soroban-poseidon/releases/tag/v25.0.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/32xxx/CVE-2026-32129.json",
        "https://github.com/stellar/rs-soroban-poseidon/security/advisories/GHSA-g2p6-hh5v-7hfm",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-32129",
        "https://github.com/stellar/rs-soroban-poseidon/pull/10"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-328"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/32xxx/CVE-2026-32129.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-32129",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 503348,
  "published_at": "2026-03-12T17:47:10.717+00:00"
}