CVE-2026-56581

Executive Summary

Business Impact: HCL MyCloud is a cloud-based file sync and share platform used across various industries including healthcare, finance, and legal. The vulnerability allows an attacker to potentially access session data or authentication tokens due to a missing Path attribute on a cookie. This increases the risk of session hijacking, potentially leading to unauthorized access to sensitive files and data stored within the MyCloud environment. The likely attacker is a remote, unauthenticated user who can trick a legitimate user into interacting with a malicious link.

Vulnerability Class & Attack Vector: This is a Cookie Attribute Path Not Set vulnerability (CWE-565). The attack vector is network-accessible but requires user interaction and high attack complexity. An attacker must be on the same network path as the victim (e.g., on a shared Wi-Fi network) or be able to inject a malicious link into a page the victim visits.

Urgency Assessment: The CVSS score of 2.6 (Low) combined with an EPSS probability of 0.0% indicates that this vulnerability is not currently being exploited in the wild and is considered low risk. However, the lack of a patch and the potential for session hijacking in a cloud file-sharing context warrants monitoring and proactive mitigation.

Key Facts:

• Vendor: HCL
• Affected Software: HCL MyCloud
• Patch Status: 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:H/PR:N/UI:R/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 access to the victim's machine.
• AC:H (High): Exploitation requires specific conditions. The attacker must be in a position to intercept or manipulate network traffic (e.g., man-in-the-middle) or trick the user into clicking a crafted link that causes the browser to send the cookie to a different path. This is not a simple, direct exploit.
• PR:N (None): The attacker does not need any prior authentication or privileges to attempt exploitation.
• UI:R (Required): The attack requires the victim to perform an action, such as clicking a malicious link or visiting a compromised website while authenticated to MyCloud.
• S:U (Unchanged): A successful attack does not change the scope of the affected component. The attacker gains access to resources within the same security authority as the victim's session.
• C:L (Low): There is a low impact on confidentiality. The attacker could potentially read session data or authentication tokens, but not necessarily all data within the application.
• I:N (None): There is no impact on integrity. The attacker cannot modify data.
• A:N (None): There is no impact on availability.

EPSS Interpretation: An EPSS probability of 0.0% means that as of the publication date, there is no evidence of active exploitation in the wild. This is consistent with the low CVSS score and the lack of public proof-of-concept code.

Historical Comparison: This vulnerability is similar to other "Cookie Attribute Not Set" issues found in web applications, such as those related to session fixation or path traversal via cookies. It is less severe than a direct SQL injection or RCE but can be a stepping stone for more significant attacks.

Temporal & Environmental Considerations: Since no patch is available, the temporal score remains unchanged. The environmental score could be higher if the MyCloud instance is exposed to the internet and used by high-value targets.

Technical Deep Dive & Attack Mechanics

Root Cause Analysis: The developer failed to set the Path attribute on a session cookie. By default, a cookie without a Path attribute is sent to the server for any request to the domain that set it. This means a cookie set for /secure could also be sent to /public if the path is not explicitly restricted.

Step-by-Step Attack Mechanics:

1. A user authenticates to HCL MyCloud at https://mycloud.example.com/.
2. The server sets a session cookie (e.g., JSESSIONID=abc123) without a Path attribute.
3. An attacker crafts a malicious link pointing to a different path on the same MyCloud server, such as https://mycloud.example.com/attacker-controlled-path.
4. The victim, while authenticated, clicks the link.
5. The victim's browser sends the JSESSIONID cookie along with the request to the attacker-controlled path.
6. If the attacker can intercept this request (e.g., via a man-in-the-middle attack or by hosting a page that logs the request), they can capture the session token.
7. The attacker can then use this token to impersonate the victim.

Attack Surface:

• Protocol: HTTP/HTTPS
• Ports: 80, 443
• Interface: Web application login and session management.

Pre-conditions:

• The victim must be authenticated to HCL MyCloud.
• The attacker must be able to deliver a crafted link to the victim.
• The attacker must be able to capture the HTTP request containing the cookie (e.g., via network sniffing or a malicious web page).

Why Standard Defenses May Fail:

• WAF: A Web Application Firewall may not flag a missing cookie attribute as malicious.
• Network Segmentation: If the attacker is on the same network segment, they can easily sniff traffic.
• HTTPS: While HTTPS encrypts the traffic, a man-in-the-middle attack (e.g., using a rogue certificate) could still allow the attacker to see the cookie.

Vulnerable vs. Patched Code Analysis

Vulnerable Code (Pseudocode):

// In a servlet or filter setting the session cookie
HttpSession session = request.getSession();
Cookie sessionCookie = new Cookie("JSESSIONID", session.getId());
// Missing: sessionCookie.setPath("/");
response.addCookie(sessionCookie);

Patched Code (Pseudocode):

HttpSession session = request.getSession();
Cookie sessionCookie = new Cookie("JSESSIONID", session.getId());
sessionCookie.setPath("/mycloud"); // Restrict cookie to the application's root path
sessionCookie.setHttpOnly(true);
sessionCookie.setSecure(true);
response.addCookie(sessionCookie);

What the Patch Changes: The patch explicitly sets the Path attribute on the cookie to the application's root context (e.g., /mycloud). This ensures the cookie is only sent to requests within that specific path, preventing it from being sent to attacker-controlled paths.

Regression Considerations: Setting the Path attribute too restrictively could break functionality if the application has multiple sub-applications that need to share the session. The path should be set to the application's root context.

Timeline & Disclosure History

• CVE Publication Date: 2026-07-21T18:17:02.047
• Estimated Discovery: Unknown, but likely discovered by a security researcher or internal HCL team.
• Disclosure Process: The CVE was published by the CNA (likely HCL or a third-party coordinator). No details on the disclosure process 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:

• Script Kiddies: Using automated tools to scan for missing cookie attributes.
• Insider Threats: An attacker with access to the internal network could easily sniff cookies.
• Low-Sophistication Attackers: The attack is relatively simple to execute once the pre-conditions are met.

Attack Campaign Context: No specific campaigns are known to be targeting this CVE.

Geographic Targeting: No specific geographic targeting is expected.

Industry Verticals Most at Risk: Any organization using HCL MyCloud for sensitive file sharing, including:

• Healthcare (HIPAA compliance)
• Legal (client confidentiality)
• Finance (regulatory compliance)

Connection to Similar Vulnerabilities: This is a classic example of a session management flaw, similar to CWE-384 (Session Fixation) and CWE-613 (Insufficient Session Expiration).

Exploitation & Lab Setup

Red Team Section

Lab Setup:

1. Environment: A local VM running a vulnerable version of HCL MyCloud (if available) or a custom Java web application that mimics the vulnerability.
2. Tools:
   • Burp Suite or OWASP ZAP (for intercepting traffic)
   • Python (for crafting malicious links)
   • A web browser (Firefox with developer tools)

Prerequisites:

• A running instance of the vulnerable application.
• A user account on the application.
• Network access to the application.

Exploitation Walkthrough:

1. Intercept Traffic: Use Burp Suite to intercept the response from the server after login.
2. Identify Cookie: Look for the Set-Cookie header. It should look like: Set-Cookie: JSESSIONID=abc123; HttpOnly; Secure Note the absence of a Path attribute.
3. Craft Malicious Link: Create a simple HTML page that makes a request to a different path on the same server:

   <img src="https://mycloud.example.com/attacker-path" width="0" height="0">
   

4. Deliver Link: Send this link to the victim (e.g., via email or a chat message).
5. Capture Cookie: Set up a listener on the attacker's server to capture the incoming request. The cookie will be included in the Cookie header.
6. Replay Session: Use the captured JSESSIONID in a new browser session to impersonate the victim.

Expected Output: The attacker successfully accesses the victim's MyCloud account without needing credentials.

Post-Exploitation: The attacker can download, upload, or delete files within the victim's account.

Blue Team Section

Detection:

• Log Entries: Look for unusual HTTP requests to paths that do not normally exist (e.g., /attacker-path).
• Network Traffic: Monitor for multiple requests from the same IP address to different paths on the MyCloud server, especially if they include a Cookie header.
• Endpoint Behavioral Indicators: A user's session being used from an unusual IP address or geographic location.

Indicators of Compromise (IOCs)

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

• Network IOCs:
  • HTTP requests to unusual paths on the MyCloud server.
  • Multiple GET requests from the same IP to different paths within a short time frame.
• HTTP Request Patterns:
  • GET /attacker-controlled-path HTTP/1.1
  • Host: mycloud.example.com
  • Cookie: JSESSIONID=abc123
• File System Artifacts: None specific to this CVE.
• Process Execution Anomalies: None specific to this CVE.
• Log Entries:
  • Web server logs showing requests to non-standard paths.
  • Application logs showing session creation from unusual IPs.

STIX-like IOC List:

Detection Engineering

YARA Rule

rule CVE-2026-56581_Detection {
    meta:
        description = "Detects exploitation of CVE-2026-56581 in Hcl MyCloud"
        author = "Valters IT Hub"
        date = "2026-07-21"
        reference = "https://www.valtersit.com/cve/cve-2026-56581"
    strings:
        $cookie_header = "Cookie: JSESSIONID="
        $set_cookie_no_path = "Set-Cookie: JSESSIONID="
        $http_request = "GET /"
    condition:
        $cookie_header and $http_request
}

Sigma Rule (SIEM)

title: CVE-2026-56581 Hcl MyCloud Cookie Path Not Set Exploitation
id: ebdbcdb8-9437-41ad-b547-ffc1a751b062
status: experimental
description: Detects HTTP requests to unusual paths on Hcl MyCloud, potentially indicating exploitation of CVE-2026-56581
author: Valters IT Hub
date: 2026-07-21
references:
    - https://www.valtersit.com/cve/cve-2026-56581
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem:
            - '/attacker-path*'
            - '/test*'
            - '/debug*'
    condition: selection
falsepositives:
    - Legitimate administrative activity or testing
level: high

Suricata IDS Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-56581 Hcl MyCloud Cookie Path Not Set Exploitation"; flow:to_server,established; content:"GET"; http_method; content:"/"; http_uri; pcre:"/^\/[a-z0-9_-]{1,10}$/"; sid:1000001; rev:1;)

Elastic (EQL) Query

sequence by source.ip
  [network where event.type == "start" and destination.port == 443 and network.protocol == "http"]
  [http where http.request.method == "GET" and http.request.uri == "/attacker-path"]

Splunk SPL Query

index=web sourcetype=access_combined
| search method=GET uri_path=/* 
| rex field=uri_path "/(?<path>[^/]+)"
| stats count by path, clientip
| where count > 5

Wazuh Rule

<rule id="100001" level="10">
  <if_sid>31100</if_sid>
  <field name="url">\.*/attacker-path</field>
  <description>CVE-2026-56581 - Hcl MyCloud Cookie Path Not Set Exploitation Attempt</description>
  <group>cve_2026_56581,</group>
</rule>

Remediation & Mitigation

Immediate Actions (0-24 hours)

• No Patch Available: Since no patch is available, implement compensating controls.
• Network-Level Mitigation:
  • Restrict access to the MyCloud application to trusted IP addresses or VPNs.
  • Use a Web Application Firewall (WAF) to block requests to unusual paths.
• Authentication/Access Control Hardening:
  • Enforce multi-factor authentication (MFA) to reduce the impact of session hijacking.
  • Implement short session timeouts.

Short-term (1-7 days)

• Configuration Hardening:
  • If possible, manually configure the application server to set the Path attribute on all cookies.
  • For Tomcat, this can be done in the context.xml file:

    <Context sessionCookiePath="/mycloud">
    

• Monitoring Implementation:
  • Deploy the detection rules provided in this report.
  • Monitor logs for unusual session activity.

Long-term

• Architecture Changes:
  • Implement a reverse proxy that can enforce cookie attributes.
  • Use token-based authentication (e.g., JWT) instead of session cookies.
• Security Control Improvements:
  • Conduct regular security code reviews.
  • Implement automated security scanning for common misconfigurations.
• Developer Training:
  • Train developers on secure session management practices, including setting cookie attributes.

Validation

• To confirm the patch was applied:
  • Use a browser's developer tools to inspect the Set-Cookie header after login. It should include a Path attribute.
  • Run a vulnerability scanner that checks for missing cookie attributes.

References & Resources

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56581
• CVE.org: https://www.cve.org/CVERecord?id=CVE-2026-56581
• Vendor advisory: See vendor security page
• OSV: https://osv.dev/vulnerability/CVE-2026-56581 (if applicable)
• Related CWE: https://cwe.mitre.org/data/definitions/565.html
• MITRE ATT&CK: https://attack.mitre.org/techniques/T1190/

Report generated by Valters IT Hub Neural Engine v25 | 2026-07-21 | https://www.valtersit.com/cve/cve-2026-56581