UBUNTU-CVE-2026-71886

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Source
https://ubuntu.com/security/CVE-2026-71886
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71886.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-71886
Upstream
Published
2026-10-05T00:00:00Z
Modified
2026-10-05T13:04:12Z
Severity
  • 8.2 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

In Bouncy Castle for Java before 1.86, the high-level OpenPGP certificate API accepted a third-party certification or trust delegation from any component key of the issuing certificate, without requiring that component to have been granted the authority to certify. OpenPGPCertificate.getCertificationBy() and getDelegationBy() resolve a third-party signature by matching its issuer key identifier against every key of the third-party certificate, then verify the issuing component's binding chain and the signature itself; nothing checked that the issuing component carried the RFC 9580 sec. 5.2.3.29 certification key flag (CERTIFY_OTHER) when the signature was created. A subkey bound only with SIGN_DATA - the online signing subkey of exactly the offline-primary arrangement those key flags exist to express - could therefore issue a positive User ID certification over an attacker-controlled identity, or a full-trust depth-one direct-key delegation of introducer trust, and the API returned it as a valid signature chain attributed to the third-party certificate. An application treating getCertificationBy(...).isValid() or getDelegationBy(...) as an identity or trusted-introducer decision would attribute the attacker's assertion to the offline primary key. The same held for a legacy RSA subkey bound only for encryption, whose algorithm is nonetheless able to sign. This does not forge the primary key's signature or recover any private key; it promotes an already-compromised restricted subkey to the primary key's identity-issuing authority, defeating the containment the key-flag separation provides. A third-party certification or delegation is now attributed to the issuing certificate only when the component key that made it is the primary key, or is a subkey holding CERTIFY_OTHER when the signature was created, so certification-capable subkeys continue to be accepted; primary keys are accepted whatever their key flags say, since a primary key is certification-capable by construction and certificates carrying no key flags subpacket at all are common. Third-party revocations are deliberately outside the rule, since declining to honour one would keep trust alive rather than withdraw it.

References

Affected packages

Ubuntu:26.04:LTS
bouncycastle

Package

Name
bouncycastle
Purl
pkg:deb/ubuntu/bouncycastle?arch=source&distro=resolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
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"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71886.json"
Ubuntu:Pro:16.04:LTS
bouncycastle

Package

Name
bouncycastle
Purl
pkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps%2Fxenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.49+dfsg-3ubuntu1
1.51-4ubuntu1
1.51-4ubuntu1+esm1

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"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71886.json"
Ubuntu:Pro:18.04:LTS
bouncycastle

Package

Name
bouncycastle
Purl
pkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps%2Fbionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.57-1
1.58-1
1.59-1
1.59-1ubuntu0.1~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"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71886.json"
Ubuntu:Pro:20.04:LTS
bouncycastle

Package

Name
bouncycastle
Purl
pkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps%2Ffocal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.61-1
1.61-1ubuntu0.1~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"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71886.json"
Ubuntu:Pro:22.04:LTS
bouncycastle

Package

Name
bouncycastle
Purl
pkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps%2Fjammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.68-2
1.68-4
1.68-5
1.68-5ubuntu0.1~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"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71886.json"
Ubuntu:Pro:24.04:LTS
bouncycastle

Package

Name
bouncycastle
Purl
pkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps%2Fnoble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.72-2
1.77-1
1.77-1ubuntu0.1~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"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71886.json"