CVE-2020-36850

Executive Summary

CVE-2020-36850 is an information disclosure vulnerability in the Sitecore JSS React Sample Application, affecting versions 11.0.0 through 14.0.1. The flaw allows page content intended for one authenticated user to be inadvertently served to another user, violating access control boundaries. This vulnerability is classified under MITRE ATT&CK tactic T1213 (Data from Information Repositories) and CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). No public proof-of-concept (PoC) or exploit code is available, and no patch has been officially released by Sitecore. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the risk remains for organizations using the affected versions in multi-tenant or user-specific content scenarios.

Supply Chain & Package Security

This vulnerability affects a Node.js/React-based application (Sitecore JSS React Sample Application), which is part of the Sitecore JavaScript Services (JSS) ecosystem. The application is typically deployed as a sample or starter template for Sitecore headless implementations. While not a direct package dependency issue (e.g., npm), the vulnerability lies in the application logic itself, specifically in how user sessions and page rendering are handled. Organizations should review their Sitecore JSS deployments and ensure they are not using the sample application in production without proper isolation.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or unassigned value. Based on the vulnerability description, a reasonable estimated CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Attacker needs a valid user account.
• User Interaction (UI): None (N) – No user action required for exploitation.
• Scope (S): Changed (C) – The vulnerable component impacts resources beyond its security scope (other users' data).
• Confidentiality (C): High (H) – Sensitive page content is disclosed.
• Integrity (I): None (N) – No data modification.
• Availability (A): None (N) – No impact on availability.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N Estimated Base Score: 6.8 (Medium)

Threat Level: Medium. The vulnerability requires authentication but can lead to significant data leakage in multi-user environments.

Deep Dive & Mechanics

The Sitecore JSS React Sample Application is designed to demonstrate headless CMS capabilities, where page content is rendered dynamically based on user context. The vulnerability arises from improper session isolation or caching mechanisms within the application. When a user requests a page, the application may incorrectly serve cached or pre-rendered content intended for another user, especially under concurrent load or when using shared rendering resources.

Root Cause: The application likely uses a shared rendering cache or session store that does not properly segregate content by user identity. For example, if the application uses a single instance of a React component that fetches data based on a user token, but the token is not correctly bound to the rendering context, another user's request may receive the previously rendered output.

Attack Vector: An authenticated attacker can trigger the vulnerability by:

1. Logging into the application with a valid account.
2. Accessing a page that contains user-specific content (e.g., dashboard, profile, or personalized data).
3. Simultaneously or sequentially, another user accesses the same page.
4. The attacker may receive the other user's content due to cache collision or session mix-up.

Impact: Disclosure of sensitive information such as personal data, internal notes, or business-critical content intended for specific users.

Vulnerable vs. Patched Code

No official patch has been released by Sitecore. However, based on the vulnerability description, the fix would involve ensuring that page rendering is strictly scoped to the authenticated user's session. Below is a conceptual example of vulnerable and patched code patterns.

Vulnerable Code (Conceptual):

// Vulnerable: Shared cache without user context
const pageCache = {};

function renderPage(pageId, user) {
  if (pageCache[pageId]) {
    return pageCache[pageId]; // Returns cached content for any user
  }
  const content = fetchContent(pageId, user);
  pageCache[pageId] = content;
  return content;
}

Patched Code (Conceptual):

// Patched: Cache key includes user ID
const pageCache = {};

function renderPage(pageId, user) {
  const cacheKey = `${user.id}:${pageId}`;
  if (pageCache[cacheKey]) {
    return pageCache[cacheKey];
  }
  const content = fetchContent(pageId, user);
  pageCache[cacheKey] = content;
  return content;
}

Note: Since no official patch exists, organizations should implement their own session isolation or disable caching for user-specific content.

Exploitation & Lab Setup

Red Team

Objective: Demonstrate information disclosure by accessing another user's page content.

Prerequisites:

• Two valid user accounts on the Sitecore JSS React Sample Application (versions 11.0.0 - 14.0.1).
• Network access to the application.

Steps:

1. Log in as User A and navigate to a page that displays user-specific content (e.g., /dashboard).
2. Note the content displayed (e.g., "Welcome, User A").
3. In a separate browser session or incognito window, log in as User B.
4. User B navigates to the same page (/dashboard).
5. If the vulnerability is present, User B may see User A's content (e.g., "Welcome, User A") instead of their own.
6. Repeat steps 1-5 with different pages and under load (e.g., rapid requests) to increase likelihood of cache collision.

No exploit code is available; this is a logic flaw that requires manual testing.

Blue Team

Detection:

• Monitor for anomalies in page content delivery, such as users reporting seeing incorrect data.
• Analyze server logs for unusual patterns: same page requested by multiple users in quick succession, or responses containing unexpected user identifiers.
• Implement session-aware logging: log the user ID associated with each page render and compare against expected values.

Prevention:

• Disable caching for any page that contains user-specific content.
• Implement strict session isolation in the rendering pipeline.
• Use a unique cache key that includes the user session ID.
• Upgrade to a patched version if Sitecore releases one.

Indicators of Compromise (IOCs)

• Log Entries: Server logs showing a user receiving content that contains another user's username, email, or other identifiers.
• Network Traffic: HTTP responses where the Set-Cookie header or response body contains mismatched user data.
• Application Errors: Error messages indicating cache key collisions or session conflicts.
• User Reports: Multiple users reporting that they see each other's data on the same page.

Detection Engineering

YARA Rule

rule CVE_2020_36850_Sitecore_JSS_Info_Disclosure {
    meta:
        description = "Detects potential exploitation of CVE-2020-36850 in Sitecore JSS React Sample Application"
        author = "Valters IT"
        date = "2025-04-17"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2020-36850"
    strings:
        $s1 = "Welcome," nocase
        $s2 = "dashboard" nocase
        $s3 = "sitecore-jss" nocase
    condition:
        all of ($s*) and filesize < 10KB
}

Sigma Rule

title: CVE-2020-36850 - Sitecore JSS Information Disclosure
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects potential exploitation of CVE-2020-36850 where page content is served to unintended users.
author: Valters IT
date: 2025-04-17
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2020-36850
logsource:
    category: webserver
    product: sitecore
detection:
    selection:
        cs-uri-query|contains: 
            - "/dashboard"
            - "/profile"
            - "/account"
        sc-status: 200
        cs-username|contains: 
            - "user"
            - "admin"
    condition: selection
falsepositives:
    - Legitimate multi-user access to shared pages
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2020-36850 Sitecore JSS Information Disclosure Attempt"; flow:to_server,established; content:"GET"; http_method; content:"/dashboard"; http_uri; content:"Welcome,"; http_server_body; nocase; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable caching for any page that renders user-specific content in the Sitecore JSS React Sample Application.
2. Implement session-aware rendering by modifying the application code to include the user session ID in cache keys (see patched code example).
3. Restrict access to the sample application to trusted users only, and avoid using it in production environments.

Long-Term Fix:

• Monitor Sitecore's official channels for a security patch. If none is released, consider migrating to a supported version of Sitecore JSS or implementing a custom fix.
• Conduct a security audit of all Sitecore JSS deployments to ensure proper session isolation.

Workarounds:

• Use a reverse proxy (e.g., Nginx) to add session-based caching headers, but this is not a complete fix.
• Implement application-level logging to detect and alert on potential information disclosure events.

Valters IT