UBUNTU-CVE-2026-71888

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Source
https://ubuntu.com/security/CVE-2026-71888
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-71888.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-71888
Upstream
Published
2026-10-05T00:00:00Z
Modified
2026-10-05T13:04:12Z
Severity
  • 8.7 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/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 streaming CMS AuthenticatedData parser accepted a message whose digestAlgorithm and authAttrs fields disagreed about whether authenticated attributes were present. RFC 5652 sec. 9.1 pairs the two, requiring that authAttrs be present whenever digestAlgorithm is, and sec. 9.2 makes the MAC cover the DER encoding of authAttrs when they are present and the eContent OCTET STRING directly when they are not. CMSAuthenticatedDataParser has to choose between those two in its constructor, before it can reach authAttrs, which comes later in the SEQUENCE, so it chose on digestAlgorithm alone: for a message with digestAlgorithm absent but authAttrs present it verified the content MAC and then returned the attributes through getAuthAttrs() as though they had been authenticated, when the MAC had never covered them. An attacker able to modify a message in transit could insert an authenticated attribute, such as an RFC 2634 ESSSecurityLabel, into an otherwise valid message while holding neither the key-encryption key nor the content-MAC key, and an application taking an authorization, routing or labelling decision from those attributes would act on attacker-chosen values. The content itself remained MAC-bound. asn1.cms.AuthenticatedData now rejects the mismatched pairing when parsing and CMSAuthenticatedDataParser cross-checks the two fields once authAttrs is read. This is a variant of CVE-2026-59642, which bound the content to the MAC for messages that legitimately carry authAttrs, and which does not address this case. This issue also affects Bouncy Castle for Java LTS before 2.73.13, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series), and bcutil-fips 2.0.8 (2.0.X series) and 2.1.8 (2.1.X series).

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-2026-71888.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-2026-71888.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-2026-71888.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-2026-71888.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-2026-71888.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-2026-71888.json"