Detect Soliton FileZen OS Command Injection Exploitation (CVE-2026-25108) in Google Chronicle
Detects exploitation of CVE-2026-25108, an OS command injection vulnerability (CWE-78) in Soliton Systems K.K FileZen file-sharing appliance. This vulnerability is listed on CISA's Known Exploited Vulnerabilities catalog and allows unauthenticated or authenticated attackers to inject arbitrary OS commands through vulnerable input fields, potentially leading to full system compromise.
MITRE ATT&CK
YARA-L Detection Query
rule cve_2026_25108_filezen_os_command_injection {
meta:
author = "df00tech Detection Engineering"
description = "Detects exploitation of CVE-2026-25108 OS command injection in Soliton FileZen"
severity = "CRITICAL"
priority = "HIGH"
reference = "https://jvn.jp/en/jp/JVN84622767/"
cve = "CVE-2026-25108"
mitre_attack_tactic = "TA0001, TA0002"
mitre_attack_technique = "T1190"
events:
(
$req.metadata.event_type = "NETWORK_HTTP"
and (
re.regex($req.network.http.target_url, `(?i)(/cgi-bin/|/admin/|/upload|/download|/login)`)
and (
re.regex($req.network.http.target_url, `[;&|` + "`" + `$(){}\[\]]`)
or re.regex($req.network.http.target_url, `(?i)(wget|curl|bash|python|perl|nc\s|/bin/sh|/etc/passwd|chmod)`)
)
)
)
or
(
$proc.metadata.event_type = "PROCESS_LAUNCH"
and $proc.target.process.command_line != ""
and re.regex($proc.target.process.command_line, `(?i)(wget|curl|nc\s|ncat|python|perl|bash\s+-[ci]|/dev/tcp|/dev/udp)`)
and $proc.principal.process.file.full_path = "/var/www/*"
)
match:
$req.principal.ip over 1h
outcome:
$risk_score = max(95)
$src_ip = array_distinct($req.principal.ip)
$target_url = array_distinct($req.network.http.target_url)
$http_method = array_distinct($req.network.http.method)
$response_code = array_distinct($req.network.http.response_code)
condition:
$req or $proc
}Chronicle YARA-L 2.0 rule detecting both the inbound HTTP injection attempt to FileZen endpoints and subsequent process execution patterns consistent with post-exploitation, with 1-hour aggregation window per source IP.
Data Sources
Required Tables
False Positives & Tuning
- Web crawlers or security scanners that probe CGI endpoints with encoded payloads during authorized testing
- Legitimate web shell management tools used by administrators that spawn child processes from web server paths
- Application update scripts initiated by the FileZen appliance from its own web server process tree
- Monitoring agents that use curl or wget to probe internal health check endpoints from the FileZen host
Other platforms for CVE-2026-25108
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1FileZen-style CGI Command Injection via HTTP GET parameter
Expected signal: Web server access log records GET request to /cgi-bin/upload.cgi with semicolon character in query string. Process audit log shows web server process (httpd/nginx) spawning /bin/sh or /bin/bash as child process executing 'id' command.
- Test 2Post-Exploitation Reverse Shell Download via Injected wget
Expected signal: Web server access log shows POST to /admin/config.cgi with pipe and wget in POST body. Network telemetry shows outbound TCP connection from web server host to ATTACKER_HOST:8080. File creation event for /tmp/payload.sh. Process execution of wget and chmod as children of web server process.
- Test 3Credential and Configuration Exfiltration via Piped cat Command
Expected signal: Web server log records GET request to /download endpoint with URL-encoded pipe and cat command sequence. Network telemetry shows outbound POST connection from FileZen host to ATTACKER_HOST:9090. Process audit captures cat /etc/passwd executed as child of web server process, followed by curl data exfiltration subprocess.
- Test 4Webshell Implantation via Command Injection for Persistent Access
Expected signal: Web server access log records POST to CGI endpoint with semicolon and echo command in body. File creation event for /var/www/html/status.php with PHP content. Process tree shows web server spawning sh executing echo redirection. Subsequent access to /var/www/html/status.php with cmd parameter would indicate webshell usage.
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