UBUNTU-CVE-2026-18040

See a problem?
Please try reporting it to the source first.
Source
https://ubuntu.com/security/CVE-2026-18040
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-18040.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-18040
Upstream
Published
2026-10-05T00:00:00Z
Modified
2026-10-05T13:04:12Z
Severity
  • 5.9 (Medium) CVSS_V4 - CVSS:4.0/AV:L/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, HQC leaked secret-derived data through two side channels: its GF(2^8) arithmetic used lookup tables indexed by field elements, making the cache line touched a function of the operand, and its fixed-weight support sampler left its duplicate scan as soon as a collision was found and stored accepted positions at a secret index. Both run on secret inputs during encapsulation and decapsulation, and the sampler re-expands the secret key from its seed on every decapsulation, so an attacker able to observe cache behaviour or decapsulation timing can recover information about the HQC private key. The field arithmetic is now table-free and the sampler branch-free within a batch of candidates, with output and randomness consumption 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-2026-18040.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-2026-18040.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-2026-18040.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-2026-18040.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-2026-18040.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-2026-18040.json"