CVE-2026-109786
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.
CVE-2026-109786
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-109786
fail2ban
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://github.com/fail2ban/fail2ban",
"vendor": "fail2ban",
"modules": [
"sshd filter"
],
"product": "fail2ban",
"versions": [
{
"status": "affected",
"version": "0.10.5",
"versionType": "custom",
"lessThanOrEqual": "1.1.1"
}
],
"platforms": [
"Linux",
"Unix"
],
"programFiles": [
"config/filter.d/sshd.conf"
],
"defaultStatus": "unknown"
}
]- Related CVEs
- CVE-2026-109786
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #28937 · Revision 1
- Added to Heist Feed
- Publisher date