CVE-2026-71891

{
  "etk_id": "ETK-2026-480",
  "cve_id": "CVE-2026-71891",
  "display_id": "CVE-2026-71891",
  "ghsa_id": "GHSA-gggh-4cvh-v637",
  "euvd_id": "EUVD-2026-92005",
  "status": "published",
  "anchor_state": "anchored",
  "title": "Improper public-key validation in BC-JAVA BLS verification",
  "summary": "BC-JAVA bcprov releases before 1.86 can incorrectly accept noncanonical BLS12-381 public keys during BLS signature verification. An attacker may cause aggregate verification to accept a signer that did not provide a matching signature when the application accepts externally constructed explicit-curve points as trusted public keys; the standard compressed-key decoding path is unaffected.",
  "mitigation": "Upgrade bcprov to version 1.86 or later. Until upgraded, accept BLS public keys only through the standard compressed-key decoding path and reject explicitly constructed noncanonical curve points.",
  "vendor": "Legion of the Bouncy Castle Inc.",
  "product": "BC-JAVA",
  "affected": [
    {
      "affected_notes": [],
      "affected_ranges": [
        ">= 1.85, < 1.86"
      ],
      "ecosystem": null,
      "fixed_versions": [
        "1.86"
      ],
      "package_name": "bcprov",
      "purl": null
    }
  ],
  "cwes": [
    347
  ],
  "cvss_score": 7.1,
  "cvss_src": "cna_vendor",
  "cvss_vector": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber",
  "epss_score": 0.0017,
  "epss_percentile": 0.0655,
  "epss_asof": "2026-10-21",
  "automation": "contextual",
  "check": true,
  "check_confidence_basis": "assessed",
  "exploit": false,
  "pipeline_minutes": 14.54200975,
  "t0_at": "2026-10-03T08:56:01.050000+00:00",
  "signals": {
    "check": {
      "at": "2026-10-03T18:22:31.164048+00:00",
      "days": 0.3934040977777778,
      "is_lower_bound": false,
      "measured_at": "2026-10-03T08:56:01.050000+00:00",
      "url": null
    },
    "trigger_signal": {
      "at": "2026-10-03T08:56:01.050000+00:00",
      "days": 0,
      "is_lower_bound": false,
      "measured_at": "2026-10-03T08:56:01.050000+00:00",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-71891"
    }
  }
}