Ed25519 identity public keys permit universal signature forgery

{
  "id": "8768997e28442fbc9479ae52cbcae502c12b146f8101fe22bab0f40d1aab5eb9",
  "url": "https://osv.dev/vulnerability/RUSTSEC-2026-0240",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Ed25519 identity public keys permit universal signature forgery",
    "summary": "All published versions of `dcrypt-sign` before 2.0.0 accepted the Edwards identity as an Ed25519 public key. A signature with `R = B` and `S = 1` then verified for every message because the challenge term multiplied the identity. The implementation also admitted other noncanonical or small-order inputs. Consumers that accepted externally supplied dcrypt Ed25519 keys may therefore have accepted forged authorizations. Version 2.0.0 replaces the custom arithmetic with `ed25519-dalek`, uses strict verification, and rejects noncanonical, small-order, and non-torsion-free public keys and `R` values, as well as noncanonical `S >= L`. No wrapper around the affected verifier is recommended as a complete workaround. Upgrade to 2.0.0 or later, audit registered keys and trust stores, and review historical actions authorized with externally supplied keys.",
    "evidence": "osv:RUSTSEC-2026-0240",
    "products": [
      {
        "name": {
          "value": "dcrypt-sign",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.0.0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "RUSTSEC-2026-0240",
      "aliases": [
        "GHSA-7j32-2mpw-c784",
        "RUSTSEC-2026-0240"
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0.0.0-0"
                },
                {
                  "fixed": "2.0.0"
                }
              ]
            }
          ],
          "package": {
            "name": "dcrypt-sign",
            "purl": "pkg:cargo/dcrypt-sign",
            "ecosystem": "crates.io"
          },
          "database_specific": {
            "cvss": null,
            "source": "https://github.com/rustsec/advisory-db/blob/osv/crates/RUSTSEC-2026-0240.json",
            "categories": [
              "crypto-failure"
            ],
            "informational": null
          },
          "ecosystem_specific": {
            "affects": {
              "os": [],
              "arch": [],
              "functions": []
            },
            "affected_functions": null
          }
        }
      ],
      "modified": "2026-10-12T18:00:14.910838740Z",
      "provider": "osv",
      "references": [
        "https://crates.io/crates/dcrypt-sign",
        "https://rustsec.org/advisories/RUSTSEC-2026-0240.html",
        "https://github.com/ioi-foundation/dcrypt/commit/c99cc86f0ee353010cd202cbcd2c310371b0bbb8",
        "https://github.com/ioi-foundation/dcrypt/releases/tag/v2.0.0"
      ],
      "provider_metadata": {
        "license": "CC0-1.0"
      }
    },
    "related_cves": [],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 306467,
  "published_at": "2026-08-09T12:00:00+00:00"
}