Vulnerability-Lookup

CVE-2026-71885 (GCVE-0-2026-71885)

Vulnerability from cvelistv5 – Published: 2026-10-03 08:51 – Updated: 2026-10-05 16:01

Title

MLS X.509 credential not bound to the LeafNode signature key

Summary

In Bouncy Castle for Java before 1.86, the Messaging Layer Security (MLS, RFC 9420) implementation did not bind an X.509 credential to a LeafNode's signature_key. LeafNode.verify() checked a leaf's signature against the signature_key carried in the leaf itself, while the credential's X.509 certificate chain was stored but never parsed or validated, so the end-entity certificate's public key was never required to match signature_key as RFC 9420 sec. 5.3 requires. A party could therefore present another party's certificate as its credential while signing the leaf, and the enclosing KeyPackage, with an unrelated key, and be accepted under that other party's identity through KeyPackage.verify() and the Group leaf-validation path. In a deployment that admits external commits without an independent credential-admission check, an unauthenticated attacker could be admitted under a victim's X.509 identity, evict the victim (resynchronization compares whole credentials rather than signing keys), derive the current epoch, decrypt subsequent group messages, and send messages accepted as the victim. TreeKEM.LeafNode now requires the end-entity certificate's subject public key, in the cipher suite's signature encoding, to equal signature_key for an X.509 credential and rejects the leaf otherwise, including an empty chain or a certificate whose key type does not match the cipher suite; certificate-chain and identity validation to a trust anchor remain the application's responsibility per RFC 9420 sec. 5.3.1. Deployments using only basic credentials are unaffected.

Severity

9.2 (Critical)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/U:Amber

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-05 16:00 UTC

CWE

CWE-295 - Improper Certificate Validation
CWE-287 - Improper Authentication

Assigner

bcorg CNA under the mitre root

CNA scorecard B 84/100 over 74 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/bcgit/bc-java/wiki/CVE%E2%80%9…	vendor-advisory
https://github.com/bcgit/bc-java/commit/77632a57e…	patch

Impacted products

1 product

Vendor	Product	Version	CPE status
Legion of the Bouncy Castle Inc.	BC-JAVA	Affected: 0 , < 1.86 (maven)	guessed

Credits

Joshua Rogers and Khaled Suliman of AISLE Research

Show details on NVD website

JSON

To clipboard

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        "assignerShortName": "bcorg",
        "cveId": "CVE-2026-71885",
        "datePublished": "2026-10-03T08:51:53.292Z",
        "dateReserved": "2026-08-08T00:06:06.982Z",
        "dateUpdated": "2026-10-05T16:01:11.470Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

CLEANSTART-2026-PP12728 (CVE-2026-71885)

Vulnerability from cleanstart – Published: 2026-10-22 00:39 – Updated: 2026-10-21 08:33 – Source website

Summary

In Bouncy Castle for Java before 1

Details

Security vulnerability affects the rundeck package. In Bouncy Castle for Java before 1.

Severity

9.2 (Critical)


                    
                      CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber

References

URL

Type

	https://github.com/cleanstart-dev/cleanstart-secu…	ADVISORY
	https://osv.dev/vulnerability/CVE-2026-71885	WEB
	https://nvd.nist.gov/vuln/detail/CVE-2026-71885	WEB

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "CleanStart",
        "name": "rundeck",
        "purl": "pkg:apk/cleanstart/rundeck"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.0-r2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "credits": [],
  "database_specific": {},
  "details": "Security vulnerability affects the rundeck package. In Bouncy Castle for Java before 1.",
  "id": "CLEANSTART-2026-PP12728",
  "modified": "2026-10-21T08:33:24Z",
  "published": "2026-10-22T00:39:36.923326Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/cleanstart-dev/cleanstart-security-advisories/tree/main/advisories/2026/CLEANSTART-2026-PP12728.json"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/CVE-2026-71885"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-71885"
    }
  ],
  "related": [],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber",
      "type": "CVSS_V4"
    }
  ],
  "summary": "In Bouncy Castle for Java before 1",
  "upstream": [
    "CVE-2026-71885"
  ]
}

FKIE_CVE-2026-71885

Vulnerability from fkie_nvd - Published: 2026-10-03 09:17 - Updated: 2026-10-06 14:49

Severity

9.2 (Critical) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/U:Amber

Summary

References

	URL	Tags
	91579145-5d7b-4cc5-b925-a0262ff19630	https://github.com/bcgit/bc-java/commit/77632a57edf350a7b5751fca1a5052daffa8dab2
	91579145-5d7b-4cc5-b925-a0262ff19630	https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071885

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://www.bouncycastle.org/download/bouncy-castle-java/",
          "defaultStatus": "unaffected",
          "modules": [
            "mls"
          ],
          "packageName": "bcmls",
          "packageURL": "pkg:maven/org.bouncycastle/bcmls-jdk18on",
          "platforms": [
            "all"
          ],
          "product": "BC-JAVA",
          "programFiles": [
            "LeafNode"
          ],
          "repo": "https://github.com/bcgit/bc-java",
          "vendor": "Legion of the Bouncy Castle Inc.",
          "versions": [
            {
              "lessThan": "1.86",
              "status": "affected",
              "version": "0",
              "versionType": "maven"
            }
          ]
        }
      ],
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In Bouncy Castle for Java before 1.86, the Messaging Layer Security (MLS, RFC 9420) implementation did not bind an X.509 credential to a LeafNode\u0027s signature_key. LeafNode.verify() checked a leaf\u0027s signature against the signature_key carried in the leaf itself, while the credential\u0027s X.509 certificate chain was stored but never parsed or validated, so the end-entity certificate\u0027s public key was never required to match signature_key as RFC 9420 sec. 5.3 requires. A party could therefore present another party\u0027s certificate as its credential while signing the leaf, and the enclosing KeyPackage, with an unrelated key, and be accepted under that other party\u0027s identity through KeyPackage.verify() and the Group leaf-validation path. In a deployment that admits external commits without an independent credential-admission check, an unauthenticated attacker could be admitted under a victim\u0027s X.509 identity, evict the victim (resynchronization compares whole credentials rather than signing keys), derive the current epoch, decrypt subsequent group messages, and send messages accepted as the victim. TreeKEM.LeafNode now requires the end-entity certificate\u0027s subject public key, in the cipher suite\u0027s signature encoding, to equal signature_key for an X.509 credential and rejects the leaf otherwise, including an empty chain or a certificate whose key type does not match the cipher suite; certificate-chain and identity validation to a trust anchor remain the application\u0027s responsibility per RFC 9420 sec. 5.3.1. Deployments using only basic credentials are unaffected."
    }
  ],
  "id": "CVE-2026-71885",
  "lastModified": "2026-10-06T14:49:40.823",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 9.2,
          "baseSeverity": "CRITICAL",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "AMBER",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber",
          "version": "4.0",
          "vulnAvailabilityImpact": "LOW",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "91579145-5d7b-4cc5-b925-a0262ff19630",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-71885",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-05T16:00:54.750454Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-03T09:17:04.730",
  "references": [
    {
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630",
      "url": "https://github.com/bcgit/bc-java/commit/77632a57edf350a7b5751fca1a5052daffa8dab2"
    },
    {
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630",
      "url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071885"
    }
  ],
  "sourceIdentifier": "91579145-5d7b-4cc5-b925-a0262ff19630",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-287"
        },
        {
          "lang": "en",
          "value": "CWE-295"
        }
      ],
      "source": "91579145-5d7b-4cc5-b925-a0262ff19630",
      "type": "Secondary"
    }
  ]
}

GHSA-JCH3-5J66-88VX

Vulnerability from github – Published: 2026-10-03 09:31 – Updated: 2026-10-03 09:31

Details

Severity

9.2 (Critical)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/U:Amber

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-71885"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-287"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-03T09:17:04Z",
    "severity": "CRITICAL"
  },
  "details": "In Bouncy Castle for Java before 1.86, the Messaging Layer Security (MLS, RFC 9420) implementation did not bind an X.509 credential to a LeafNode\u0027s signature_key. LeafNode.verify() checked a leaf\u0027s signature against the signature_key carried in the leaf itself, while the credential\u0027s X.509 certificate chain was stored but never parsed or validated, so the end-entity certificate\u0027s public key was never required to match signature_key as RFC 9420 sec. 5.3 requires. A party could therefore present another party\u0027s certificate as its credential while signing the leaf, and the enclosing KeyPackage, with an unrelated key, and be accepted under that other party\u0027s identity through KeyPackage.verify() and the Group leaf-validation path. In a deployment that admits external commits without an independent credential-admission check, an unauthenticated attacker could be admitted under a victim\u0027s X.509 identity, evict the victim (resynchronization compares whole credentials rather than signing keys), derive the current epoch, decrypt subsequent group messages, and send messages accepted as the victim. TreeKEM.LeafNode now requires the end-entity certificate\u0027s subject public key, in the cipher suite\u0027s signature encoding, to equal signature_key for an X.509 credential and rejects the leaf otherwise, including an empty chain or a certificate whose key type does not match the cipher suite; certificate-chain and identity validation to a trust anchor remain the application\u0027s responsibility per RFC 9420 sec. 5.3.1. Deployments using only basic credentials are unaffected.",
  "id": "GHSA-jch3-5j66-88vx",
  "modified": "2026-10-03T09:31:18Z",
  "published": "2026-10-03T09:31:18Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-71885"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bcgit/bc-java/commit/77632a57edf350a7b5751fca1a5052daffa8dab2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071885"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber",
      "type": "CVSS_V4"
    }
  ]
}

OPENSUSE-SU-2026:12090-1

Vulnerability from csaf_opensuse - Published: 2026-10-09 00:00 - Updated: 2026-10-10 08:44

Summary

bouncycastle-1.86-1.1 on GA media

Severity

Moderate

Scope

14 vulnerabilities in this advisory, including CVE-2026-71885.

CVE-2026-71885

7.7 (High)


                
                  CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

Recommended: 32 products

Open the full advisory

UBUNTU-CVE-2026-71885 (CVE-2026-71885)

Vulnerability from osv_ubuntu – Published: 2026-10-03 09:17 – Updated: 2026-10-17 09:49 – Source website

Details

Severity

9.2 (Critical)


                    
                      CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/U:Amber

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-71885	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-71885	REPORT
	https://github.com/bcgit/bc-java/wiki/CVE%E2%80%9…	REPORT
	https://github.com/bcgit/bc-java/commit/77632a57e…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libbcmail-java",
            "binary_version": "1.51-4ubuntu1+esm1"
          },
          {
            "binary_name": "libbcpg-java",
            "binary_version": "1.51-4ubuntu1+esm1"
          },
          {
            "binary_name": "libbcpkix-java",
            "binary_version": "1.51-4ubuntu1+esm1"
          },
          {
            "binary_name": "libbcprov-java",
            "binary_version": "1.51-4ubuntu1+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "bouncycastle",
        "purl": "pkg:deb/ubuntu/bouncycastle@1.51-4ubuntu1+esm1?arch=source\u0026distro=esm-apps/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.49+dfsg-3ubuntu1",
        "1.51-4ubuntu1",
        "1.51-4ubuntu1+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libbcmail-java",
            "binary_version": "1.59-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcpg-java",
            "binary_version": "1.59-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcpkix-java",
            "binary_version": "1.59-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcprov-java",
            "binary_version": "1.59-1ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "bouncycastle",
        "purl": "pkg:deb/ubuntu/bouncycastle@1.59-1ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.57-1",
        "1.58-1",
        "1.59-1",
        "1.59-1ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libbcmail-java",
            "binary_version": "1.61-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcpg-java",
            "binary_version": "1.61-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcpkix-java",
            "binary_version": "1.61-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcprov-java",
            "binary_version": "1.61-1ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "bouncycastle",
        "purl": "pkg:deb/ubuntu/bouncycastle@1.61-1ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.61-1",
        "1.61-1ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libbcmail-java",
            "binary_version": "1.68-5ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcpg-java",
            "binary_version": "1.68-5ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcpkix-java",
            "binary_version": "1.68-5ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcprov-java",
            "binary_version": "1.68-5ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbctls-java",
            "binary_version": "1.68-5ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:22.04:LTS",
        "name": "bouncycastle",
        "purl": "pkg:deb/ubuntu/bouncycastle@1.68-5ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.68-2",
        "1.68-4",
        "1.68-5",
        "1.68-5ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libbcjmail-java",
            "binary_version": "1.77-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcmail-java",
            "binary_version": "1.77-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcpg-java",
            "binary_version": "1.77-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcpkix-java",
            "binary_version": "1.77-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcprov-java",
            "binary_version": "1.77-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbctls-java",
            "binary_version": "1.77-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libbcutil-java",
            "binary_version": "1.77-1ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:24.04:LTS",
        "name": "bouncycastle",
        "purl": "pkg:deb/ubuntu/bouncycastle@1.77-1ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.72-2",
        "1.77-1",
        "1.77-1ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libbcjmail-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcmail-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcpg-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcpkix-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcprov-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbctls-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcutil-java",
            "binary_version": "1.80-3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.10",
        "name": "bouncycastle",
        "purl": "pkg:deb/ubuntu/bouncycastle@1.80-3?arch=source\u0026distro=stonking"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.80-3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libbcjmail-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcmail-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcpg-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcpkix-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcprov-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbctls-java",
            "binary_version": "1.80-3"
          },
          {
            "binary_name": "libbcutil-java",
            "binary_version": "1.80-3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "bouncycastle",
        "purl": "pkg:deb/ubuntu/bouncycastle@1.80-3?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.80-3"
      ]
    }
  ],
  "aliases": [],
  "details": "In Bouncy Castle for Java before 1.86, the Messaging Layer Security (MLS, RFC 9420) implementation did not bind an X.509 credential to a LeafNode\u0027s signature_key. LeafNode.verify() checked a leaf\u0027s signature against the signature_key carried in the leaf itself, while the credential\u0027s X.509 certificate chain was stored but never parsed or validated, so the end-entity certificate\u0027s public key was never required to match signature_key as RFC 9420 sec. 5.3 requires. A party could therefore present another party\u0027s certificate as its credential while signing the leaf, and the enclosing KeyPackage, with an unrelated key, and be accepted under that other party\u0027s identity through KeyPackage.verify() and the Group leaf-validation path. In a deployment that admits external commits without an independent credential-admission check, an unauthenticated attacker could be admitted under a victim\u0027s X.509 identity, evict the victim (resynchronization compares whole credentials rather than signing keys), derive the current epoch, decrypt subsequent group messages, and send messages accepted as the victim. TreeKEM.LeafNode now requires the end-entity certificate\u0027s subject public key, in the cipher suite\u0027s signature encoding, to equal signature_key for an X.509 credential and rejects the leaf otherwise, including an empty chain or a certificate whose key type does not match the cipher suite; certificate-chain and identity validation to a trust anchor remain the application\u0027s responsibility per RFC 9420 sec. 5.3.1. Deployments using only basic credentials are unaffected.",
  "id": "UBUNTU-CVE-2026-71885",
  "modified": "2026-10-17T09:49:44Z",
  "published": "2026-10-03T09:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-71885"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-71885"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071885"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/bcgit/bc-java/commit/77632a57edf350a7b5751fca1a5052daffa8dab2"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/U:Amber",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-71885"
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Publication & reservation Sightings KEV catalogs Other timestamps

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-71885 (GCVE-0-2026-71885)

CLEANSTART-2026-PP12728 (CVE-2026-71885)

FKIE_CVE-2026-71885

GHSA-JCH3-5J66-88VX

OPENSUSE-SU-2026:12090-1

UBUNTU-CVE-2026-71885 (CVE-2026-71885)

Tags

Sightings

Nomenclature

Vulnerability timeline

Related by attack behaviour