CVE-2024-10086: HashiCorp Consul XSS Vulnerability

CVE-2024-10086 Overview

A reflected Cross-Site Scripting (XSS) vulnerability has been identified in HashiCorp Consul and Consul Enterprise. The vulnerability arises from the server response not explicitly setting a Content-Type HTTP header, which allows user-provided inputs to be misinterpreted by browsers and leads to reflected XSS attacks. This flaw could enable attackers to execute arbitrary JavaScript code in the context of a victim's browser session when they interact with crafted malicious links.

Critical Impact

Attackers can exploit this vulnerability to execute malicious scripts in users' browsers, potentially leading to session hijacking, credential theft, or unauthorized actions performed on behalf of authenticated users within Consul environments.

Affected Products

• HashiCorp Consul (Community Edition)
• HashiCorp Consul Enterprise
• NetApp products utilizing HashiCorp Consul (see NetApp Security Advisory)

Discovery Timeline

• October 30, 2024 - CVE-2024-10086 published to NVD
• January 10, 2025 - Last updated in NVD database

Technical Details for CVE-2024-10086

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The root issue lies in how the Consul server handles HTTP responses during error conditions.

When the Consul server returns error responses, it fails to explicitly set the Content-Type HTTP header. This omission allows browsers to perform MIME type sniffing, potentially interpreting user-controlled input as executable content such as HTML or JavaScript. In certain error scenarios where user input is reflected in the response body, this behavior can be exploited to execute arbitrary scripts.

The network-based attack vector requires user interaction, as victims must click on or navigate to a maliciously crafted URL. The vulnerability can affect resources beyond the scope of the vulnerable component, potentially impacting other applications sharing the same browser session or domain trust relationships.

Root Cause

The vulnerability stems from insufficient HTTP response header configuration in the Consul server. Specifically, the application does not set an explicit Content-Type header (such as text/plain or application/json) when returning error responses. Without this header, browsers fall back to content sniffing behavior defined in their MIME Sniffing algorithms, which can incorrectly interpret text responses containing HTML-like content as executable HTML/JavaScript.

Attack Vector

The attack requires an attacker to craft a malicious URL containing XSS payload that targets a Consul endpoint which reflects user input in error messages. When a victim clicks the link, the Consul server returns an error response without a proper Content-Type header. The browser's MIME sniffing interprets the response as HTML, executing the embedded malicious JavaScript in the context of the victim's session.

The vulnerability is exploited through network requests and requires the victim to interact with the malicious link, making it a reflected XSS attack scenario. Successful exploitation can lead to limited confidentiality and integrity impacts, allowing attackers to access session tokens, modify displayed content, or perform actions as the authenticated user.

Detection Methods for CVE-2024-10086

Indicators of Compromise

• Unusual HTTP requests to Consul endpoints containing encoded JavaScript payloads or HTML entities
• Web server logs showing requests with suspicious URL parameters containing <script> tags or event handlers
• Reports from users about unexpected browser behavior or pop-ups when accessing Consul-related URLs

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing common XSS patterns targeting Consul endpoints
• Monitor Consul access logs for requests with URL-encoded script tags (%3Cscript%3E) or JavaScript event handlers (onerror, onload)
• Deploy Content Security Policy (CSP) headers at the reverse proxy or load balancer level to mitigate XSS execution even if injection occurs
• Enable SentinelOne Singularity XDR for endpoint-level detection of post-exploitation activities resulting from XSS attacks

Monitoring Recommendations

• Review Consul server access logs regularly for anomalous request patterns, particularly those with unusual query parameters
• Monitor for new or unexpected JavaScript execution contexts within browser sessions interacting with Consul
• Implement network traffic analysis to identify potential XSS exploitation attempts targeting Consul services

How to Mitigate CVE-2024-10086

Immediate Actions Required

• Upgrade HashiCorp Consul and Consul Enterprise to patched versions as specified in the HashiCorp Security Advisory
• Implement reverse proxy or load balancer rules to add explicit Content-Type headers to all Consul responses
• Restrict direct access to Consul UI and API endpoints, requiring authentication and limiting exposure to trusted networks only
• Deploy Content Security Policy headers to prevent inline script execution as a defense-in-depth measure

Patch Information

HashiCorp has released security updates to address this vulnerability. Administrators should consult the official HashiCorp Security Advisory HCSEC-2024-24 for specific version information and upgrade instructions. Organizations using NetApp products that incorporate Consul should also review the NetApp Security Advisory NTAP-20250110-0006 for relevant guidance.

Workarounds

• Deploy a reverse proxy (such as NGINX or HAProxy) in front of Consul that enforces Content-Type: application/json or Content-Type: text/plain headers on all responses
• Implement strict Content Security Policy headers (Content-Security-Policy: default-src 'self') at the network edge to prevent inline script execution
• Restrict Consul UI and API access to authenticated users only and limit network exposure through firewall rules

# Example NGINX configuration to add Content-Type header
# Add to location block handling Consul traffic
location /consul/ {
    proxy_pass http://consul-backend:8500/;
    proxy_hide_header Content-Type;
    add_header Content-Type "application/json" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header Content-Security-Policy "default-src 'self'" always;
}