DEBIAN-CVE-2026-109786

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Source
https://security-tracker.debian.org/tracker/CVE-2026-109786
Import Source
https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-109786.json
JSON Data
https://api.osv.dev/v1/vulns/DEBIAN-CVE-2026-109786
Upstream
Published
2026-10-13T03:16:40Z
Modified
2026-10-13T11:00:08Z
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
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

Debian:12 / fail2ban

Package

Name
fail2ban
Purl
pkg:deb/debian/fail2ban?arch=source&distro=bookworm

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
1.1.0-1
1.1.0-2
1.1.0-3
1.1.0-4
1.1.0-6
1.1.0-7
1.1.0-8
1.1.0-9
1.1.0-10
1.1.0-11
1.1.1-1

Ecosystem specific 

{
    "urgency":  "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-109786.json"

Debian:13 / fail2ban

Package

Name
fail2ban
Purl
pkg:deb/debian/fail2ban?arch=source&distro=trixie

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
1.1.0-10
1.1.0-11
1.1.1-1

Ecosystem specific 

{
    "urgency":  "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-109786.json"

Debian:14 / fail2ban

Package

Name
fail2ban
Purl
pkg:deb/debian/fail2ban?arch=source&distro=forky

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
1.1.0-10
1.1.0-11
1.1.1-1

Ecosystem specific 

{
    "urgency":  "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-109786.json"