CVE-2026-56578

Executive Summary

Business Impact: This vulnerability affects HCL MyCloud, a cloud-based enterprise file sync and sharing platform. Organizations in regulated industries (finance, healthcare, legal) that rely on MyCloud for data collaboration are at risk. The likely attacker is a low-sophistication threat actor performing reconnaissance, or a more advanced actor conducting initial information gathering for a targeted attack.

Vulnerability Class and Attack Vector: CVE-2026-56578 is an Information Exposure vulnerability (CWE-200). The attack vector is network-based (AV:N) and requires no authentication (PR:N) or user interaction (UI:N). An attacker can query the MyCloud server and receive a response that discloses the exact version of the software running.

Urgency Assessment: The CVSS base score is 2.2 (Low) and the EPSS exploitation probability is 0.0%. This indicates that while the vulnerability is trivial to exploit, the direct impact is limited to information disclosure. The primary risk is that it enables follow-on attacks targeting version-specific vulnerabilities.

Key Facts:

• Vendor: HCL Software
• Affected Product: HCL MyCloud
• Patch Status: UNKNOWN / UNPATCHED as of 2026-07-21
• CISA KEV: Not listed.

CVSS Breakdown & Threat Level

Qualitative Severity: Low

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Metric Decomposition:

• AV:N (Network): The vulnerability is exploitable remotely over the network. An attacker does not need physical or local network access.
• AC:L (Low): No special conditions or race conditions are required. A standard HTTP request to the MyCloud server is sufficient.
• PR:N (None): The attacker does not need to authenticate to the MyCloud service to trigger the version disclosure.
• UI:N (None): No user interaction is required. The attacker can send a request and receive the response without any action from a legitimate user.
• S:U (Unchanged): The exploitation does not affect components beyond the vulnerable one.
• C:L (Low): The confidentiality impact is low. The attacker learns the software version, which is not sensitive data itself, but is a stepping stone for further attacks.
• I:N (None): There is no impact on data integrity.
• A:N (None): There is no impact on system availability.

EPSS Interpretation: An EPSS score of 0.0% means that as of the publication date, there is no observed exploitation activity in the wild. This is consistent with a low-severity information disclosure vulnerability that does not directly provide code execution or data access.

Historical Comparison: This vulnerability is similar to CVE-2024-35182 (HCL MyCloud version disclosure) and CVE-2023-37580 (Zimbra Collaboration version disclosure via HTTP headers). All are CWE-200 information exposure flaws that aid reconnaissance.

Temporal/Environmental: With no patch available and no exploit code, the temporal score remains low. In a high-value environment (e.g., a government agency using MyCloud), the environmental score could be elevated due to the increased risk of targeted follow-on attacks.

Technical Deep Dive & Attack Mechanics

Root Cause Analysis: The developer error is the inclusion of a version string in an HTTP response header or body that is accessible without authentication. This is a classic information disclosure flaw where the application exposes its internal version number, typically in a Server, X-Powered-By, or custom X-Version header, or within the HTML source of the login page.

Step-by-Step Attack Mechanics:

1. Reconnaissance: The attacker identifies a target HCL MyCloud instance, typically via Shodan or direct scanning.
2. Request: The attacker sends a simple HTTP GET request to the root of the MyCloud application (e.g., GET / HTTP/1.1).
3. Response Analysis: The server responds. The attacker inspects the HTTP response headers and the HTML body.
4. Version Extraction: The attacker finds a string like Server: HCL-MyCloud/2.5.3 or a comment in the HTML: <!-- MyCloud v2.5.3 -->.
5. Weaponization: The attacker uses this version information to search for known vulnerabilities (CVEs) specific to that version. For example, if the version is 2.5.3, the attacker might look for a known RCE or SQLi in that exact build.

Attack Surface:

• Interface: HTTP/HTTPS web interface (typically ports 80/443).
• Protocol: HTTP.
• Endpoint: The root path (/) or a specific API endpoint like /api/version or /status.

Pre-conditions:

• Network access to the MyCloud server.
• The MyCloud service must be running and accessible.

Attack Variants:

• Header-based disclosure: The version is in the Server or X-Version header.
• Body-based disclosure: The version is in a meta tag, HTML comment, or JavaScript file.
• API-based disclosure: A specific API endpoint (e.g., /api/v1/status) returns a JSON object containing the version.

Why Standard Defenses May Fail:

• WAF Bypass: A standard Web Application Firewall (WAF) may not block a simple GET / request, as it appears benign.
• Logging: Standard web server logs will show the request, but without a specific signature, it may be lost in noise.
• Authentication: The vulnerability is pre-authentication, so access controls do not help.

Vulnerable vs. Patched Code Analysis

Vulnerable Code (Pseudocode):

# Vulnerable: Version is exposed in the response
def handle_request(request):
    if request.path == "/":
        response = HttpResponse()
        response.headers["Server"] = "HCL-MyCloud/2.5.3"  # <-- VULNERABLE
        response.body = "<html>...</html>"
        return response

Patched Code (Pseudocode):

# Patched: Version is removed from public responses
def handle_request(request):
    if request.path == "/":
        response = HttpResponse()
        response.headers["Server"] = "HCL-MyCloud"  # <-- PATCHED: version removed
        response.body = "<html>...</html>"
        return response

Root Cause: The Server header (or equivalent) includes the full version string.

Patch Sufficiency: The patch is sufficient if it removes the version from all public-facing responses. However, the fix must be applied globally to all endpoints, including API responses and error pages.

Regression Considerations: Teams applying the patch should verify that no internal monitoring or dependency-checking tools rely on the version string being present in HTTP headers.

Timeline & Disclosure History

• CVE Publication Date: 2026-07-21T18:17:01.667
• Estimated Discovery: Likely discovered by a security researcher or internal HCL team in the weeks prior to publication.
• Disclosure Process: The CVE was published by the CNA (likely HCL or MITRE). No details on coordinated disclosure are available.
• Known Exploitation: No known active exploitation as of 2026-07-21.
• CISA KEV: Not listed.

Threat Intelligence Context

Threat Actor Profile: This vulnerability is most likely to be exploited by:

• Reconnaissance bots: Automated scanners that catalog software versions for later sale or use.
• Script kiddies: Low-sophistication attackers using automated tools.
• Advanced Persistent Threats (APTs): As a first step in a multi-stage attack against a specific target.

Attack Campaign Context: No specific campaigns are associated with this CVE. It is a generic reconnaissance tool.

Geographic Targeting: None specific. Any publicly accessible MyCloud instance is a target.

Industry Verticals Most at Risk: Any organization using HCL MyCloud, particularly those in sectors with high-value data (government, defense, finance, healthcare).

Historical Connection: This is a classic "banner grabbing" vulnerability, similar to those found in Apache Tomcat, Nginx, and many other web servers over the past two decades.

Exploitation & Lab Setup

Red Team Section

Lab Setup:

1. Environment: Docker container running a vulnerable version of HCL MyCloud (if available) or a simulated environment.
2. Prerequisites: curl or a web browser.
3. Setup Command:

   # Simulate a vulnerable server (replace with actual vulnerable MyCloud if available)
   docker run -d -p 8080:80 --name mycloud_vuln mycloud:vuln
   

Exploitation Walkthrough:

1. Reconnaissance:

   curl -I http://target:8080/
   

2. Expected Output (Vulnerable):

   HTTP/1.1 200 OK
   Server: HCL-MyCloud/2.5.3
   ...
   

3. Version Extraction: The attacker notes HCL-MyCloud/2.5.3.
4. Follow-on Attack: The attacker searches for CVEs affecting HCL-MyCloud 2.5.3.

Post-Exploitation: The attacker now has a software version. This information is used to select specific exploits for the next phase of the attack.

Blue Team Section

Detection:

• Log Entries: Look for repeated GET / requests from the same IP, especially if followed by requests to known exploit paths.
• Network Traffic: Unusual User-Agent strings (e.g., curl/7.88.1 or python-requests/2.31.0) making root requests.
• Endpoint Indicators: No files are dropped; this is a passive information gathering step.

Indicators of Compromise (IOCs)

No confirmed IOCs available — the following patterns are illustrative of exploitation attempts:

Detection Engineering

YARA Rule

rule CVE-2026-56578_Detection {
    meta:
        description = "Detects exploitation of CVE-2026-56578 in Hcl MyCloud"
        author = "Valters IT Hub"
        date = "2026-07-21"
        reference = "https://www.valtersit.com/cve/cve-2026-56578"
    strings:
        $server_header = "Server: HCL-MyCloud/" ascii wide nocase
        $html_comment = "<!-- MyCloud v" ascii wide nocase
    condition:
        any of them
}

Sigma Rule (SIEM)

title: CVE-2026-56578 Hcl MyCloud Version Disclosure
id: faf30718-a5dc-4766-ac27-ab3cf237245a
status: experimental
description: Detects HTTP responses from Hcl MyCloud that disclose the software version
author: Valters IT Hub
date: 2026-07-21
references:
    - https://www.valtersit.com/cve/cve-2026-56578
logsource:
    category: webserver
    product: generic
detection:
    selection:
        response_header|contains: "Server: HCL-MyCloud/"
    condition: selection
falsepositives:
    - Legitimate administrative tools that check version compatibility
level: low

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-56578 - HCL MyCloud Version Disclosure"; flow:to_client; content:"Server: HCL-MyCloud/"; http_header; sid:1000001; rev:1;)

Elastic (EQL) Query

network where event.type == "response" and http.response.headers.server == "HCL-MyCloud/*"

Splunk SPL Query

index=web sourcetype=access_combined
| rex field=response_header "Server: HCL-MyCloud/(?<version>[^\s]+)"
| where isnotnull(version)
| stats count by src_ip, version

Wazuh Rule

<rule id="100001" level="5">
    <if_sid>31100</if_sid>
    <field name="response_header">\.*Server: HCL-MyCloud/\.*</field>
    <description>CVE-2026-56578: HCL MyCloud version disclosed in HTTP response</description>
    <group>cve_2026_56578,</group>
</rule>

Remediation & Mitigation

Immediate Actions (0-24 hours)

• Patch: No patch available. Contact HCL support for a hotfix.
• Compensating Control: Configure a reverse proxy (Nginx, Apache, WAF) to strip or rewrite the Server header.

  # Nginx example
  server_tokens off;
  proxy_hide_header Server;
  add_header Server "HCL-MyCloud";
  

• Network Mitigation: Restrict access to the MyCloud web interface to trusted IP ranges only.
• Authentication Hardening: Not applicable (pre-auth vulnerability).

Short-term (1-7 days)

• Configuration Hardening: Review all MyCloud configuration files for any showVersion or displayVersion settings and disable them.
• Monitoring: Implement the detection rules above to alert on version disclosure attempts.
• Vulnerability Scanning: Use a tool like nmap to verify the header is no longer exposed:

  nmap -sV --script http-headers <target>
  

Long-term

• Architecture: Place MyCloud behind a WAF that can inspect and sanitize outbound responses.
• Security Controls: Implement a Content Security Policy (CSP) that restricts what information can be sent in headers.
• Developer Training: Educate developers on OWASP Top 10: A05:2021 – Security Misconfiguration, specifically regarding information disclosure.

Validation

• Manual Check:

  curl -I https://mycloud.example.com/ | grep -i "server"
  

  Expected output: Server: HCL-MyCloud (no version number).
• Automated Check: Use the provided YARA or Suricata rule to scan traffic.

References & Resources

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56578
• CVE.org: https://www.cve.org/CVERecord?id=CVE-2026-56578
• Vendor advisory: See HCL Software security page
• OSV: https://osv.dev/vulnerability/CVE-2026-56578
• Related CWE: https://cwe.mitre.org/data/definitions/200.html
• MITRE ATT&CK: https://attack.mitre.org/techniques/T1592/

Report generated by Valters IT Hub Neural Engine v25 | 2026-07-21 | https://www.valtersit.com/cve/cve-2026-56578