UBUNTU-CVE-2026-109786

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Source
https://ubuntu.com/security/CVE-2026-109786
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-109786
Upstream
Published
2026-10-15T00:00:00Z
Modified
2026-10-17T12:58:03Z
Severity
  • 5.3 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

In fail2ban 0.10.5 through 1.1.1 before ddd879d, the sshd filter (config/filter.d/sshd.conf) accepts an "on " suffix after the host address. Because OpenSSH logs the offered username verbatim, a remote unauthenticated attacker can use a username such as "x VICTIM-SOURCE-IP-ADDRESS on" to make fail2ban associate failed login attempts with an arbitrary source IP address and ban it (e.g., to block logins from a legitimate user). The default filter mode is affected.

References

Affected packages

Ubuntu:22.04:LTS
fail2ban

Package

Name
fail2ban
Purl
pkg:deb/ubuntu/fail2ban?arch=source&distro=jammy

Affected ranges

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

Affected versions

0.*
0.11.2-2
0.11.2-4
0.11.2-5
0.11.2-6

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "fail2ban",
            "binary_version":  "0.11.2-6"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json"
Ubuntu:24.04:LTS
fail2ban

Package

Name
fail2ban
Purl
pkg:deb/ubuntu/fail2ban?arch=source&distro=noble

Affected ranges

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

Affected versions

1.*
1.0.2-2
1.0.2-3
1.0.2-3ubuntu0.1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "fail2ban",
            "binary_version":  "1.0.2-3ubuntu0.1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json"
Ubuntu:26.04:LTS
fail2ban

Package

Name
fail2ban
Purl
pkg:deb/ubuntu/fail2ban?arch=source&distro=resolute

Affected ranges

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

Affected versions

1.*
1.1.0-8
1.1.0-9

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "fail2ban",
            "binary_version":  "1.1.0-9"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json"
Ubuntu:26.10
fail2ban

Package

Name
fail2ban
Purl
pkg:deb/ubuntu/fail2ban?arch=source&distro=stonking

Affected ranges

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

Affected versions

1.*
1.1.0-9
1.1.0-10
1.1.0-11

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "fail2ban",
            "binary_version":  "1.1.0-11"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json"
Ubuntu:Pro:14.04:LTS
fail2ban

Package

Name
fail2ban
Purl
pkg:deb/ubuntu/fail2ban?arch=source&distro=esm-infra-legacy%2Ftrusty

Affected ranges

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

Affected versions

0.*
0.8.10-3
0.8.11~pre1+git29-gccd2657-1
0.8.11-1
0.8.11-1ubuntu0.1~esm1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "fail2ban",
            "binary_version":  "0.8.11-1ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json"
Ubuntu:Pro:16.04:LTS
fail2ban

Package

Name
fail2ban
Purl
pkg:deb/ubuntu/fail2ban?arch=source&distro=esm-apps%2Fxenial

Affected ranges

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

Affected versions

0.*
0.9.3-1
0.9.3-1ubuntu0.1~esm1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "fail2ban",
            "binary_version":  "0.9.3-1ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json"
Ubuntu:Pro:18.04:LTS
fail2ban

Package

Name
fail2ban
Purl
pkg:deb/ubuntu/fail2ban?arch=source&distro=esm-apps%2Fbionic

Affected ranges

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

Affected versions

0.*
0.9.7-2
0.10.2-1
0.10.2-2
0.10.2-2ubuntu0.1~esm1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "fail2ban",
            "binary_version":  "0.10.2-2ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json"
Ubuntu:Pro:20.04:LTS
fail2ban

Package

Name
fail2ban
Purl
pkg:deb/ubuntu/fail2ban?arch=source&distro=esm-apps%2Ffocal

Affected ranges

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

Affected versions

0.*
0.10.2-2.1
0.11.1-1
0.11.1-1ubuntu0.1~esm1

Ecosystem specific 

{
    "binaries":  [
        {
            "binary_name":  "fail2ban",
            "binary_version":  "0.11.1-1ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-109786.json"