UBUNTU-CVE-2026-18036

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Source
https://ubuntu.com/security/CVE-2026-18036
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-18036.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-18036
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:H/AT:P/PR:N/UI:N/VC:H/VI:N/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, NTRU reduced secret values with the % operator in three helpers whose reference implementations are deliberately division-free, so each reduction was carried out by an integer division whose latency depends on the secret operand. Polynomial.modQ divided by a variable divisor, which a compiler cannot strength-reduce to a multiply the way it can a constant one, so it emitted a division on every call including on the decapsulation path where the dividend derives from the private key; Polynomial.mod3 and NTRUSampling.mod3 divided the secret key polynomials f and g during key generation, the message polynomials r and m during encapsulation, and coefficients recovered during decapsulation. An attacker able to measure that timing can recover information about the NTRU private key. modQ now masks, which is exact because q is always a power of two, and mod3 uses the reference implementation's division-free fold and select; the results are unchanged.

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-2026-18036.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-2026-18036.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-2026-18036.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-2026-18036.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-2026-18036.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-2026-18036.json"