CVE-2020-25849

CVE-2020-25849 — Openfind MailGates/MailAudit Command Injection

Executive Summary

CVE-2020-25849 is a command injection vulnerability in Openfind MailGates and MailAudit, two enterprise email security and archiving gateway products. An authenticated attacker who has obtained a valid user access token can exploit a flaw in the cgi parameter to inject and execute arbitrary system commands on the underlying server. With a CVSS score of 8.8 and an EPSS percentile of 81.1%, this vulnerability represents a significant post-authentication RCE risk to organizations running affected versions. A patch is claimed to be available in version 5.2.8.048, but this has not been independently confirmed, and no public evidence of exploitation or proof-of-concept code has been identified.

Technical Analysis

The NVD description states that MailGates and MailAudit products contain a command injection flaw that "can be used to inject and execute system commands from the cgi parameter after attackers obtain the user's access token." This phrasing implies a post-authentication attack surface, meaning the vulnerability is reachable only after the attacker has valid credentials or a valid session token.

The affected component is a CGI handler. The flaw class is command injection, which typically occurs when user-controlled input is passed to a system shell call (e.g., system(), exec(), popen(), or equivalent) without adequate sanitization, escaping, or parameterization. In this case, the injected content originates from the cgi parameter — this is the only specific parameter named in the description and should be treated as the sole known detail.

Several aspects remain unclear from the available data:

• Affected versions: The Affected Versions field is empty. Only the patch version (5.2.8.048) is provided, allowing inference that versions prior to this patch are likely vulnerable, but this is not confirmed.

• Authentication model: The description mentions "user's access token," suggesting a token-based session mechanism. The exact token type (API key, JWT, session cookie) and where it is presented (HTTP header, cookie, query parameter) are not specified.

• CGI parameter context: Whether the cgi parameter is a page identifier, action dispatcher, or filename that gets concatenated into a shell command remains unknown. Insufficient technical detail is available to confirm the exact injection point mechanism.

Attack surface: The products — MailGates and MailAudit — are deployed as email gateway appliances handling inbound/outbound mail flow. They are typically internet-facing or at minimum act as the perimeter for inbound email, meaning the web management/API interface may be exposed on the network boundary. The fact that the attacker must first obtain a user's access token reduces the remote exploitability window, though token theft via other means (phishing, credential stuffing, session hijacking, other CVEs) would chain into this flaw.

The vulnerability mechanism can be summarized as: attacker obtains a valid access token → attacker crafts a request where the cgi parameter contains operating system command syntax → the server concatenates the input into a shell command without adequate filtering → the attacker's command executes with the privileges of the web server/application process.

Exploitation Scenarios

No public PoC exists for CVE-2020-25849; the following attack chain is inferred from the vulnerability class and the description provided. Any specific implementation details not present in the NVD data are deliberately omitted.

Step 1 — Reconnaissance and target identification: An attacker identifies Openfind MailGates or MailAudit instances exposed on the internet or internal networks. This can be accomplished via search engine dorks identifying the product's login pages, or through network scanning for characteristic ports and HTTP banners. Shodan queries such as title:"MailGates" or title:"MailAudit" can surface exposed management interfaces.

Step 2 — Access token acquisition: The attacker must first obtain a legitimate user's access token. This could be achieved through:

• Phishing or spear-phishing to steal credentials from mail users.
• Credential stuffing against the user portal using previously breached credentials.
• Session fixation or session hijacking via an adjacent vulnerability.
• Insider access with minimal privileges.
• Default credentials (though no evidence exists that such credentials are present in these products).

Step 3 — Command injection trigger: With the access token in hand, the attacker sends a crafted HTTP request to the vulnerable CGI endpoint that processes the cgi parameter. The request is constructed so that the cgi parameter value contains both the legitimate expected content and injected operating system command syntax (e.g., shell metacharacters such as ;, |, &&, or backticks, followed by an operating system command). Because the product passes this parameter value to a system shell without adequate sanitization, the injected command is executed alongside the intended operation.

Since no public PoC exists and no code-level details are available, the exact injection syntax, URI path, and HTTP method cannot be specified. The attack must be understood at the vulnerability-class level: unvalidated user input flowing into a shell execution context.

Step 4 — Post-exploitation impact: Successful exploitation grants the attacker arbitrary command execution on the mail gateway server with the privileges of the application process (often root or a highly privileged service account in appliance-like deployments). Post-exploitation activities may include:

• Data exfiltration: Reading email archives, audit logs, and configuration files containing credentials.
• Lateral movement: Pivoting from the mail gateway into the internal network, as mail gateways often have network trust relationships with directory services and other mail infrastructure.
• Persistent access: Installing web shells, backdoors, or establishing outbound connections for command-and-control.
• Email interception and manipulation: Modifying mail flow rules to intercept or redirect sensitive communications.
• Environment destruction: Wiping logs and disrupting mail services to cover tracks.

The CVSS score of 8.8 (High) reflects the network access vector (implied), low attack complexity, and high confidentiality, integrity, and availability impact once the token requirement is met.

Impact Assessment

CVSS analysis: The reported CVSS base score is 8.8 (High). While the exact vector string is unavailable, the score magnitude on the 0–10 scale strongly suggests:

• Attack vector: Network (AV:N) — remote exploitation over the network.
• Attack complexity: Low (AC:L) — no special conditions required beyond valid token.
• Privileges required: Low (PR:L) — consistent with "user's access token" requirement.
• User interaction: None (UI:N).
• Confidentiality/Integrity/Availability impact: High (C:H/I:H/A:H) — arbitrary system command execution implies full compromise of the hosting server.

These characteristics yield 8.8 under CVSS v3.x when (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) is applied.

Business impact:

• Email integrity breach: MailGates and MailAudit sit at the center of an organization's email security posture. Full command execution on these appliances can allow attackers to read, alter, forward, or delete email traffic, undermining compliance obligations (e.g., legal discovery, regulatory retention).
• Credential exposure: Configuration stores, directory service integration credentials (LDAP bind accounts), database credentials, and admin passwords may reside on these systems. Compromise of these secrets enables broader domain access.
• Lateral movement: Mail gateways frequently have privileged network paths into the domain controller environment for directory lookups. A compromised mail gateway can be a springboard for domain compromise.
• Availability: Mail is a mission-critical system. Attacker disruption of the gateway can halt all inbound/outbound email, causing business discontinuity.

Blast radius: The direct blast radius is the single appliance host. However, because mail gateway appliances contain the keys to the kingdom (email content, administrative credentials, directory service integration), the effective blast radius extends to the entire mail domain and downstream systems that rely on mail integrity.

EPSS consideration: The EPSS score of 0.02231 (81.1st percentile) indicates a relatively high probability of exploitation in the wild relative to all known CVEs. While this is not evidence of active exploitation (CISA KEV does not list this CVE), it suggests that attackers are likely aware of and may be attempting to exploit this class of vulnerability.

Detection Guidance

Sigma Rule

The following Sigma rule detects HTTP requests to MailGates/MailAudit that contain shell metacharacters in the cgi parameter, indicating possible command injection attempts.

title: Openfind MailGates/MailAudit Command Injection Attempt
id: 9a8c4efc-12a4-4a78-9b2d-9e4c23a61d09
status: experimental
description: Detects command injection attempts in the cgi parameter of MailGates and MailAudit web interfaces.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2020-25849
author: Valtersit Threat Intelligence
date: 2024/01/15
tags:
    - attack.privilege-escalation
    - attack.t1190
    - cve.2020-25849
logsource:
    category: webserver
    product: apache
    definition: 'Web server access log for MailGates/MailAudit appliance'
detection:
    selection:
        cs-uri-query|contains:
            - 'cgi='
    injection_patterns:
        cs-uri-query|contains:
            - '%3B'          # URL-encoded semicolon
            - '%7C'          # URL-encoded pipe
            - '%26%26'       # URL-encoded &&
            - ';'
            - '|'
            - '&&'
            - '`'
            - '$('
    condition: selection and injection_patterns
falsepositives:
    - Legitimate uses of semicolons or pipes in CGI query strings (low likelihood)
    - Security scanners testing for the vulnerability
level: high

YARA Rule

The following YARA rule scans captured HTTP traffic, log dumps, or PCAP-derived content for payload patterns associated with command injection attempts targeting the cgi parameter.

rule CVE_2020_25849_Openfind_Command_Injection {
    meta:
        author = "Valtersit Threat Intelligence"
        description = "Detects command injection payload patterns targeting Openfind MailGates/MailAudit cgi parameter"
        cve = "CVE-2020-25849"
        date = "2024-01-15"
        severity = "high"
    strings:
        $cgi_param = "cgi=" ascii wide nocase
        $semicolon = ";" ascii wide
        $pipe = "|" ascii wide
        $andand = "&&" ascii wide
        $backtick = "`" ascii wide
        $dollar_paren = "$(" ascii wide
        $cmd_whoami = "whoami" ascii wide nocase
        $cmd_id = "id;" ascii wide nocase
        $cmd_uname = "uname" ascii wide nocase
        $cmd_cat = "cat" ascii wide nocase
        $cmd_etc = "/etc/passwd" ascii wide nocase
    condition:
        $cgi_param and (
            $semicolon or $pipe or $andand or $backtick or $dollar_paren
        ) and (
            # of ($cmd_*) >= 1
        )
}

Suricata IDS Rule

The following Suricata rule detects inbound HTTP requests to MailGates/MailAudit management interfaces containing shell metacharacters in query strings with the cgi parameter.

alert http any any -> $HOME_NET any (
    msg:"CVE-2020-25849 - Openfind MailGates/MailAudit Command Injection Attempt";
    flow:established,to_server;
    http.uri;
    content:"cgi=";
    nocase;
    pcre:"/cgi=[^&]*(?:;|\||&&|`|\$\(|%3B|%7C|%26%26)/i";
    classtype:attempted-admin;
    reference:cve,2020-25849;
    reference:url,nvd.nist.gov/vuln/detail/CVE-2020-25849;
    sid:2024021501;
    rev:1;
    metadata:created_at 2024_01_15, updated_at 2024_01_15;
)

Elastic Detection

The following Elastic EQL rule correlates web server logs to identify requests containing both the cgi parameter and command injection signatures.

sequence by host.name, source.ip
    with maxspan=5m
    [ network where event.category == "web" and
      network.protocol == "http" and
      url.query like~ "%cgi=*" ]
    [ process where event.category == "process" and
      /* Command execution events from the web application process */
      process.parent.name like~ "httpd*" or
      process.parent.name like~ "apache*" or
      process.parent.name like~ "java*" ]

Splunk SPL Query

The following Splunk query indexes web access logs and flags requests containing command injection signatures in the cgi parameter.

index=web sourcetype=iis OR sourcetype=access_combined
| where like(uri_query, "%cgi=%")
| eval has_injection=if(match(uri_query, "(?i)(cgi=[^&]*(;|\||&&|`|\$\(|%3B|%7C|%26%26))"), 1, 0)
| where has_injection=1
| rex field=uri_query "cgi=(?<cgi_value>[^&]*)"
| stats count by src_ip, uri, cgi_value, _time
| sort - _time
| table _time, src_ip, uri, cgi_value, count
| rename src_ip as "Source IP", cgi_value as "Injected CGI Value", count as "Attempt Count"

Wazuh OSSEC Rule

The following Wazuh local rule detects command injection signatures in web server logs for MailGates/MailAudit.

<group name="web, attack, command_injection,">
    <rule id="100305" level="10">
        <decoded_as>web</decoded_as>
        <description>Openfind MailGates/MailAudit Command Injection Attempt (CVE-2020-25849)</description>
        <field name="url" type="pcre2">(?i)cgi=[^&]*(;|\||&&|`|\$\(|%3B|%7C|%26%26)</field>
        <group>web_application_attack,command_injection,</group>
        <mitre>
            <id>T1190</id>
        </mitre>
        <cve>CVE-2020-25849</cve>
        <info>Possible command injection attempt in MailGates/MailAudit cgi parameter from $srcip to $url</info>
    </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED — single source claims patch, not independently confirmed).

The CNA claims that version 5.2.8.048 fixes the vulnerability. However, this patch claim has not been independently confirmed through public analysis, vendor advisory cross-referencing, or reproducibility testing. Organizations should verify patch availability with Openfind directly before deployment.

1. Immediate mitigations (before patching):

• Restrict network access: Limit access to the MailGates/MailAudit web management interface to trusted administrative networks only. Do not expose the management interface directly to the internet.
• Enforce multi-factor authentication (MFA) for all user accounts that can authenticate to MailGates/MailAudit, reducing the risk of access token theft via credential compromise.
• Monitor and rotate access tokens: Audit active sessions and rotate access tokens/session keys, especially if any credential compromise is suspected.
• Deploy web application firewall (WAF) rules that block query strings containing shell metacharacters in the cgi parameter (as in the Suricata rule above).
• Privilege minimization: Run the web application process with the least privilege necessary; prevent the mail gateway web UI from running as root if possible.

2. Patch/upgrade steps:

• Contact Openfind support to confirm the availability and integrity of version 5.2.8.048.
• Review the upgrade notes and pre-upgrade checklist provided by the vendor.
• Schedule maintenance window: upgrading a mail gateway will cause mail flow interruption.
• Backup the current configuration and mail store before proceeding.
• Apply the patch to version 5.2.8.048 following the vendor's documented procedure.
• Verify all web interface functionality post-upgrade; confirm the cgi parameter no longer accepts shell metacharacters.
• If the patch cannot be obtained or deployed immediately, continue with the immediate mitigations above.

3. Long-term hardening:

• Establish a configuration baseline for mail gateway appliances: disabled unnecessary services, hardened TLS configuration, account lockout policies.
• Implement network segmentation: place mail gateway appliances in a DMZ with no direct outbound internet access except to required services (e.g., DNS, mail relays).
• Integrate appliance logs into the SIEM for continuous monitoring (per the detection rules above).
• Conduct periodic penetration testing focused on mail infrastructure, specifically targeting authenticated command injection and related vulnerability classes (e.g., OS command injection, LDAP injection, path traversal).
• Maintain an asset inventory of all mail gateway deployments and track patch status centrally.
• Subscribe to the vendor's security advisories and promptly evaluate future patches.

References

1. NVD Entry: CVE-2020-25849 — https://nvd.nist.gov/vuln/detail/CVE-2020-25849
2. MITRE ATT&CK: T1190 — Exploit Public-Facing Application — https://attack.mitre.org/techniques/T1190/
3. Openfind Product Page: MailGates/MailAudit official documentation — https://www.openfind.com/en/ (verify product-specific advisory page)
4. EPSS Data: FIRST EPSS score for CVE-2020-25849 — https://www.first.org/epss/
5. CISA KEV: CVE-2020-25849 is not listed in the Known Exploited Vulnerabilities catalog (as of the last check) — https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Exploitation in the wild: No known threat actor campaigns or in-the-wild exploitation evidence has been publicly documented for CVE-2020-25849 at the time of writing. The EPSS percentile (81.1%) indicates elevated interest relative to other vulnerabilities, but this metric reflects probabilistic modeling rather than confirmed exploitation. The absence of CISA KEV listing further suggests no federal-level confirmed exploit activity. However, the absence of public evidence does not rule out targeted exploitation by advanced actors, particularly in regions where Openfind products are widely used (primarily Asia-Pacific).