CVE-2023-25915

CVE-2023-25915 — Authenticated Remote Command Execution in Danfoss AK-SM800A

Executive Summary

CVE-2023-25915 is a critical vulnerability in the Danfoss AK-SM800A supervisory controller, a device used in commercial refrigeration and HVAC monitoring systems. An authenticated remote attacker can exploit improper input validation to execute arbitrary operating system commands on the target device with elevated privileges.

The vulnerability carries a CVSS score of 9.9 (Critical), reflecting the combination of network accessibility, low attack complexity, and full impact on confidentiality, integrity, and availability. The affected device is deployed in industrial/OT environments (supermarkets, cold storage facilities), making successful exploitation a direct threat to operational continuity. Patch confidence is partial — only a version upgrade to 3.3 is recommended, with no confirmed vendor patch advisory.

Technical Analysis

The CVE is classified under CWE-20 (Improper Input Validation). The NVD description states: "Due to improper input validation, an authenticated remote attacker could execute arbitrary commands on the target system."

Vulnerability Mechanism: The Danfoss AK-SM800A controller accepts user-supplied input through its management interface. Certain input fields or parameters are not adequately validated or sanitized before being passed to a command interpreter. This lack of validation allows a remote authenticated user to inject operating system commands, which are then executed with the privileges of the underlying service process.

Attack Surface: The attack surface includes all network-accessible functions of the AK-SM800A that require authentication. This includes but is not limited to the web-based management interface, configuration endpoints, and any maintenance or diagnostic functions that process user-supplied data. Because authentication is required, the attacker must first compromise or possess valid credentials.

Technical Details: Specific function names, endpoint paths, and parameter names are not disclosed in the NVD description or CNA title. Insufficient technical detail is available to provide a code-level walkthrough. The vulnerability class is command injection via improper input validation, which typically manifests in one of the following ways:

1. System command concatenation: User input is concatenated into a shell command without proper escaping or validation.
2. Command substitution: User input is passed to a system call (e.g., system(), exec(), popen()) without sanitization.
3. Injection via embedded scripting: User input is interpreted by a scripting engine that supports OS command execution.

Affected Scope: The vulnerability affects the Danfoss AK-SM800A supervisory controller. The device is typically deployed in retail refrigeration and cold storage environments, managing temperature control, alarm systems, and energy monitoring for multiple refrigeration units.

Exploitation Scenarios

Prerequisites for exploitation:

• Network access to the AK-SM800A management interface
• Valid credentials (username/password) for an authenticated session
• The device is running a vulnerable firmware version (prior to 3.3)

Attack Chain:

Step 1 — Reconnaissance / Target Identification: The attacker first identifies Danfoss AK-SM800A devices exposed on the network. Attackers may use Shodan or similar scanning tools with filters for Danfoss industrial devices, or scan internal network segments for the device's management web interface. Successful identification requires network visibility to the device's management port.

Step 2 — Authentication: The attacker must authenticate to the device. This can be achieved via:

• Default or weak credentials (common in OT environments)
• Credential stuffing using breached password databases
• Phishing or social engineering of facility management staff

Step 3 — Triggering the Vulnerability: Once authenticated, the attacker accesses the vulnerable input parameter through the management interface. The attacker submits a specially crafted payload containing OS command syntax (e.g., command separators like ;, &&, |, or command substitution operators) embedded in the input field. Because the application performs improper input validation, the malicious payload is accepted and processed.

Step 4 — Execution and Post-Exploitation Impact: The injected command executes with the privileges of the device's service process. Potential post-exploitation actions include:

• Exfiltration of device configuration and credentials
• Modification of refrigeration control parameters (temperature setpoints, alarm thresholds)
• Enabling persistent backdoor access via new user accounts or modified configurations
• Lateral movement into the broader OT network using the compromised device as a pivot point
• Disruption of refrigeration control, potentially causing product loss (spoilage) or safety incidents

PoC Status: No public proof-of-concept or exploit code has been identified. The attack chain above is inferred from the vulnerability class (command injection via improper input validation) and the NVD description. No public exploit-in-the-wild evidence has been reported at the time of writing.

Impact Assessment

Business Impact: The Danfoss AK-SM800A is a critical component in commercial refrigeration infrastructure. Successful exploitation allows an attacker to execute arbitrary commands, yielding full compromise of the device. The impact transcends typical IT breaches — it directly affects OT systems that control physical environments.

Affected Systems:

• Danfoss AK-SM800A supervisory controllers running firmware versions prior to 3.3
• Devices deployed in supermarkets, cold storage facilities, food processing plants, and pharmaceutical storage

Blast Radius: The CVSS score of 9.9 (Critical) reflects:

• Privileges Required: Low (PR:L) — only low-privileged access is needed to trigger the vulnerability
• User Interaction: None (UI:N) — no user interaction required beyond the initial authentication
• Scope: Changed (S:C) — the compromised component (application) impacts resources beyond its security authority (underlying OS)
• Confidentiality Impact: High — attacker can read system files, configuration data, and credentials
• Integrity Impact: High — attacker can modify system configurations, firmware, and control parameters
• Availability Impact: High — attacker can disrupt operations, disable the device, or cause industrial process failures

SCADA/OT Context: The AK-SM800A may interface with multiple refrigeration units, sensors, and alarm systems. Compromise of this supervisory controller could allow attackers to:

• Suppress alarm notifications (masking unsafe conditions)
• Alter temperature setpoints (causing product spoilage)
• Disable safety interlocks
• Use the device as a foothold for deeper OT network penetration

Detection Guidance

The following detection rules are provided to assist security teams in identifying exploitation attempts against Danfoss AK-SM800A devices. These rules focus on the command injection behavior and unusual authenticated activity patterns.

Sigma Rule

title: Danfoss AK-SM800A Command Injection Attempt
id: 4f2b8e3a-9c12-4d8f-a3b1-6e7c2d9f0a11
status: experimental
description: Detects potential command injection attempts against Danfoss AK-SM800A supervisory controller via authenticated interface, correlated with command execution indicators.
author: valtersit.com Threat Intelligence
date: 2024/01/15
logsource:
  category: webserver
  product: unknown
detection:
  selection:
    c-uri|contains:
      - ';'
      - '|'
      - '&&'
      - '`'
      - '$('
      - '%3B'
      - '%7C'
      - '%26%26'
      - '%60'
      - '%24%28'
    c-uri|contains:
      - 'cmd'
      - 'exec'
      - 'system'
      - 'shell'
  condition: selection
  timeframe: 5m
fields:
  - src_ip
  - user
  - c-uri
falsepositives:
  - Legitimate device configuration containing semicolons or pipes in data fields
  - Maintenance operations with valid command syntax
level: high
tags:
  - attack.t1210
  - attack.execution
  - cve.2023-25915

YARA Rule

rule Danfoss_AK_SM800A_Command_Injection_Payload
{
    meta:
        author = "valtersit.com Threat Intelligence"
        description = "Detects command injection payloads targeting Danfoss AK-SM800A"
        cve = "CVE-2023-25915"
        severity = "critical"
        date = "2024-01-15"

    strings:
        $cmd_sep1 = ";"
        $cmd_sep2 = "|"
        $cmd_sep3 = "&&"
        $cmd_sep4 = "`"
        $cmd_sub1 = "$("
        $cmd_sep_enc1 = "%3B"
        $cmd_sep_enc2 = "%7C"
        $cmd_keyword1 = "whoami" ascii nocase
        $cmd_keyword2 = "id" ascii nocase
        $cmd_keyword3 = "cat" ascii nocase
        $cmd_keyword4 = "uname" ascii nocase
        $cmd_keyword5 = "wget" ascii nocase
        $cmd_keyword6 = "curl" ascii nocase
        $danfoss_ref1 = "AK-SM800A" ascii nocase
        $danfoss_ref2 = "AK-SM" ascii nocase

    condition:
        ($danfoss_ref1 or $danfoss_ref2) and
        (any of ($cmd_sep*) or any of ($cmd_sep_enc*)) and
        (
            any of ($cmd_keyword*) or
            #cmd_sep1 >= 2 or
            #cmd_sep3 >= 1
        )
}

Suricata IDS Rule

alert http any any -> $DANFOSS_AK_SM800A any (msg:"CVE-2023-25915 Danfoss AK-SM800A Command Injection Attempt"; flow:established,to_server; content:"POST"; http_method; content:"AK-SM"; http_uri; nocase; pcre:"/(?:;|\||&&|`|\$\().*(?:whoami|id|cat|uname|wget|curl|nc|ncat|sh|bash|csh)/Ui"; classtype:attempted-admin; reference:cve,2023-25915; reference:url,https://nvd.nist.gov/vuln/detail/CVE-2023-25915; sid:10025915; rev:1; priority:1;)

Explanation: This rule matches HTTP POST requests to URI paths containing "AK-SM" that include both command separators (semicolon, pipe, ampersand, backtick, dollar-paren) and common Unix command keywords. It triggers on network traffic before the request reaches the device.

Elastic Detection

sequence by source.ip with maxspan=15m
  [network where event.action == "connection_attempted" and destination.port == 80 and destination.ip != "10.0.0.0/8"]
  [http where event.dataset == "nginx.access" and url.path contains "AK-SM" and 
   (user_agent.name == "curl" or user_agent.name == "wget" or 
    url.query contains ";" or url.query contains "|" or 
    url.query contains "&&" or url.query contains "$(")]
  [process where event.action == "exec" and process.parent.name == "embedded_httpd" or process.parent.name == "server" ]

Note: The parent process name is speculative based on typical embedded device architectures. Adjust based on actual observed parent processes from your environment.

Splunk SPL Query

index=network sourcetype=weblog
| where like(uri, "%AK-SM%")
| rex field=uri "(?<cmd_separators>[;\|\&]|\$\()"
| stats count by src_ip, uri, user, _time
| where count > 3
| append
    [ search index=network sourcetype=weblog uri="*AK-SM*"
      | rex field=uri "(?<cmd_keywords>(?i)(whoami|id|cat|uname|wget|curl|sh|bash))"
      | where isnotnull(cmd_keywords) ]
| table _time, src_ip, user, uri, cmd_separators, cmd_keywords
| sort - _time

Wazuh OSSEC Rule

<rule id="100259" level="15">
  <if_sid>31100</if_sid>
  <decoded_as>web</decoded_as>
  <match>AK-SM</match>
  <regex>(\;|\||\&\&|`|\$\()\s*(whoami|id|cat|uname|wget|curl|sh|bash)</regex>
  <description>Danfoss AK-SM800A command injection attempt (CVE-2023-25915)</description>
  <group>attack_execution,cve_2023_25915,</group>
  <mitre>
    <id>T1210</id>
  </mitre>
</rule>

Mitigation & Patch Guidance

Patch Confidence: 1/4 (PARTIAL) — A workaround/mitigation (firmware version 3.3) is available, but no official vendor patch advisory has been confirmed.

Immediate Mitigations (days 0–7):

1. Upgrade firmware to version 3.3 to the distribution channel — this is the recommended mitigation per the available patch data.
2. If immediate upgrade is not possible, restrict network access to the AK-SM800A management interface to trusted administrative hosts only, via firewall rules.
3. Disable remote management interfaces when not in use, or restrict them to the local OT network segment.
4. Enforce strong, unique credentials for all user accounts on the device. Replace default passwords immediately.
5. Monitor authentication logs for unusual activity, especially failed login attempts followed by successful logins from unexpected IP addresses.

Patch/Upgrade Steps:

1. Verify the current firmware version on all AK-SM800A devices.
2. Contact Danfoss technical support or access the vendor portal to obtain firmware version 3.3.
3. Schedule maintenance windows for firmware upgrades; test in a staging environment before production rollout.
4. Verify firmware integrity and signature authentication before applying.
5. Document the upgrade procedure and update device inventories.

Long-Term Hardening (weeks 1–8):

1. Segment OT and IT networks — place AK-SM800A on isolated VLANs with strict access control lists.
2. Deploy network-based detection using the Suricata and Sigma rules provided above.
3. Implement centralized logging for all AK-SM800A management traffic; forward to SIEM.
4. Establish an OT asset inventory — maintain current firmware versions, patch levels, and support status for all ICS devices.
5. Develop a credential management policy for OT devices; implement password rotation procedures.
6. Subscribe to Danfoss security advisories and monitor CISA ICS advisories for this product line.
7. Implement MFA where supported for all administrative access to OT infrastructure.
8. Periodic vulnerability scanning of the OT network segment to identify misconfigurations and unpatched devices.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2023-25915 — Official CVE record with NVD description and scoring.
2. CISA ICS Advisories (suggested monitoring): https://www.cisa.gov/news-events/ics-advisories — Monitor for Danfoss-related ICS certification advisories.
3. Danfoss Product Page (AK-SM800A): https://www.danfoss.com — Vendor product documentation and firmware distribution.
4. MITRE ATT&CK — T1210: https://attack.mitre.org/techniques/T1210/ — Exploitation of Remote Services tactic reference.
5. CVE.org: https://www.cve.org/CVERecord?id=CVE-2023-25915 — CVE entry with CNA-provided metadata.

Threat Actor Activity Note: No threat actor campaigns or exploit-in-the-wild evidence have been publicly reported for CVE-2023-25915 at the time of writing. EPSS score (0.00777) indicates low probability of exploitation in the near term (52.4th percentile among known exploited vulnerabilities); the CVE is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog. However, given the critical CVSS score and the OT nature of the device, monitoring and patching should be prioritized.

Report prepared by valtersit.com Threat Intelligence. This report is based on the CVE Intelligence Data provided above. All technical specifics are derived from the NVD description and CNA title; where technical detail was insufficient, vulnerability-class-level analysis is provided without fabrication of implementation details.