{
  "cveId": "CVE-2026-71890",
  "url": "https://patchblox.com/security/cve/CVE-2026-71890",
  "summary": "CVE-2026-71890 is fixed in bouncycastle on 1 platform, first by DEBIAN-CVE-2026-71890, released October 3, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "bouncycastle: In Bouncy Castle for Java before 1.86, validation of an MLS (RFC 9420) external commit\u0027s proposal list, org.bouncycas...",
  "description": "In Bouncy Castle for Java before 1.86, validation of an MLS (RFC 9420) external commit\u0027s proposal list, org.bouncycastle.mls.protocol.Group.validateExternalCachedProposals, counted the proposals by type and bounded the removed leaf index but never established that the removed leaf had anything to do with the joiner. RFC 9420 sec. 12.2 permits at most one Remove proposal in an external commit, with which the joiner removes an old version of themselves, and requires that where one is present the LeafNode in the commit\u0027s path field meet the criteria it would have to meet in an Update for the removed leaf, in particular that its credential present identifiers acceptable for the removed participant. The ordinary proposal-list validator\u0027s self-remove rule is deliberately not applied on this path, because a resync commit legitimately removes a leaf the joiner owns, but nothing was put in its place. Any party holding the group\u0027s public GroupInfo, which is precisely what an external joiner is meant to be given, could therefore commit a Remove naming any member\u0027s LeafIndex and have every member apply it, evicting that member and taking over their slot in the ratchet tree. The credential check that should have prevented this existed only in the gRPC interop harness and so protected no other caller of the public Group.externalJoin and Group.handle API. An external commit carrying a Remove is now accepted only when the removed leaf\u0027s credential is identical to the one in the joiner\u0027s own new leaf, on both the sending and the receiving side.",
  "published": "2026-10-03T09:17:05Z",
  "severity": "",
  "epss": 0.00249,
  "epssPercentile": 0.16329,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "bouncycastle",
      "release": "Debian 14",
      "fixedVersion": "1.86-1",
      "fix": "DEBIAN-CVE-2026-71890",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-71890",
      "released": "2026-10-03T21:16:35Z"
    },
    {
      "platform": "linux",
      "product": "bouncycastle",
      "release": "opensuse-leap 16.0",
      "fixedVersion": "1.86-160000.1.1",
      "fix": "OPENSUSE-SU-2026:22169-1",
      "url": "https://patchblox.com/security/fix/linux/opensuse-su-2026-22169-1",
      "released": "2026-11-07T00:47:19Z"
    },
    {
      "platform": "linux",
      "product": "bouncycastle",
      "release": "sles 15.6",
      "fixedVersion": "1.86-150200.3.41.1",
      "fix": "SUSE-SU-2026:4797-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-4797-1",
      "released": "2026-11-07T00:42:08Z"
    },
    {
      "platform": "linux",
      "product": "bouncycastle",
      "release": "sles 15.7",
      "fixedVersion": "1.86-150200.3.41.1",
      "fix": "SUSE-SU-2026:4797-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-4797-1",
      "released": "2026-11-07T00:42:08Z"
    },
    {
      "platform": "linux",
      "product": "bouncycastle",
      "release": "sles 16.0",
      "fixedVersion": "1.86-160000.1.1",
      "fix": "SUSE-SU-2026:24461-1",
      "url": "https://patchblox.com/security/fix/linux/suse-su-2026-24461-1",
      "released": "2026-11-07T00:44:01Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T06:59:42Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}