Sophos SG UTM WebAdmin Remote Code Execution (RCE) Vulnerability Advisory (CVE-2020-25223)
Executive & SecOps Summary
SECOPS ASSESSMENTSophos SG UTM versions prior to v9.705 MR5, v9.607 MR7, and v9.511 MR11 with WebAdmin enabled
Unauthenticated remote attackers can execute arbitrary OS commands with root privileges by sending specially crafted HTTP requests
Immediately upgrade to patched firmware versions (v9.705 MR5, v9.607 MR7, v9.511 MR11 or later) and restrict external access to WebAdmin (TCP 4444)
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Apply the official firmware updates provided by Sophos immediately. Access the UTM CLI via SSH and execute the following commands to check and apply updates:
# Log in as root via SSH and check for available firmware updates
audit_firmware_packages --check
# Download and install the latest firmware update (may require a system reboot)
/sbin/auisys.plx --run2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict access to the WebAdmin interface (default TCP 4444) so that it is only accessible from trusted internal management networks.
# Restrict WebAdmin access (TCP 4444) to a trusted administrator IP (e.g., 192.168.10.50)
iptables -A INPUT -p tcp -s 192.168.10.50 --dport 4444 -j ACCEPT
iptables -A INPUT -p tcp --dport 4444 -j DROP3. Log Audit & IoC Verification Commands
Inspect the WebAdmin logs for any suspicious command injection attempts or anomalous session requests.
# Search WebAdmin logs for suspicious shell metacharacters (backticks, semicolons, pipes)
grep -E '(\||;|`|\$\()' /var/log/httpd.log
# Verify the current Sophos UTM firmware version
cc get system versionStop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
Eliminate public-facing VPN concentrators and firewall management ports with identity-first Zero-Trust Network Access.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2020-25223) is an OS Command Injection vulnerability (CWE-78) residing in the WebAdmin management interface of Sophos SG UTM appliances. The root cause lies in the insufficient input validation and sanitization of user-supplied parameters, such as session identifiers (SIDs), processed by the WebAdmin backend. This allows unauthenticated remote attackers to inject malicious shell commands directly into the system execution context.
2. Exploitation Mechanics & Attack Scenario
An attacker targeting an exposed WebAdmin port (default TCP 4444) can craft a malicious HTTP request containing shell metacharacters (such as backticks '`' or semicolons ';') within the SID or other input parameters. When the backend CGI scripts or APIs process this request without proper escaping, the injected payload is executed by the system shell under the context of the high-privileged WebAdmin process (root), leading to complete system compromise.
3. Infrastructure & Business Impact
Sophos SG UTM serves as a critical perimeter security gateway for enterprise networks. This vulnerability is highly critical, as evidenced by its inclusion in the CISA KEV catalog and an EPSS score of 0.9675 (top 1% of threat likelihood). Successful exploitation allows attackers to gain full administrative control over the firewall, enabling lateral movement into the internal network, traffic sniffing, credential theft, and potential deployment of ransomware.
Official Vendor Advisories & References
A remote code execution vulnerability exists in the WebAdmin of Sophos SG UTM before v9.705 MR5, v9.607 MR7, and v9.511 MR11
Frequently Asked SecOps Questions (CVE-2020-25223)
FAQQ1. How critical is CVE-2020-25223 and is it actively exploited in the wild?
CVE-2020-25223 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 96.8%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-25223?
Primary impacted vendors include sophos across sg_utm, utm_firmware. Scope summary: Sophos SG UTM versions prior to v9.705 MR5, v9.607 MR7, and v9.511 MR11
Q3. What temporary mitigations or workarounds exist for CVE-2020-25223 before patching?
[Mitigation] Immediately upgrade to patched firmware versions (v9.705 MR5, v9.607 MR7, v9.511 MR11 or later) and restrict external access to WebAdmin (TCP 4444) Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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