CVE-2024-27982: Node.js HTTP Request Smuggling Vulnerability

CVE-2024-27982 Overview

CVE-2024-27982 is an HTTP Request Smuggling vulnerability affecting the HTTP server component in Node.js. The flaw exists in how the Node.js HTTP parser handles malformed headers, specifically when a space character is placed before a Content-Length header. This improper parsing allows attackers to smuggle a second HTTP request within the body of the first request, potentially bypassing security controls, poisoning web caches, or hijacking other users' requests.

Critical Impact

Attackers can exploit this vulnerability to bypass front-end security controls, perform cache poisoning attacks, hijack other users' requests, or gain unauthorized access to sensitive data through HTTP request smuggling techniques.

Affected Products

• Node.js HTTP Server (recent versions)
• Systems running Node.js-based web applications behind reverse proxies
• Applications relying on Node.js HTTP parsing for request handling

Discovery Timeline

• 2024-05-07 - CVE-2024-27982 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2024-27982

Vulnerability Analysis

This vulnerability is classified as CWE-444 (Inconsistent Interpretation of HTTP Requests), commonly known as HTTP Request Smuggling. The root cause lies in how Node.js's HTTP server parses incoming request headers differently than front-end servers or proxies might parse them.

When a space character precedes the Content-Length header name (e.g., Content-Length: 50 instead of Content-Length: 50), Node.js fails to properly interpret this header. The server either ignores the malformed header or processes it inconsistently compared to other HTTP implementations in the request chain.

This parsing discrepancy enables attackers to craft requests where the front-end server and Node.js back-end disagree about request boundaries. By exploiting this disagreement, an attacker can inject a second, hidden request that gets processed by the back-end server while the front-end believes it's still part of the first request's body.

Root Cause

The vulnerability stems from insufficient validation and normalization of HTTP header names in Node.js's HTTP parser. According to HTTP specifications, header names should not contain leading whitespace. However, the Node.js HTTP server implementation failed to properly reject or handle headers with leading spaces, creating an inconsistency with how other HTTP components process the same request.

The parser's lenient handling of the space-prefixed Content-Length header meant that it would not recognize the header as a valid content-length indicator, potentially defaulting to Transfer-Encoding or other methods to determine the request body size, while upstream servers correctly parsed the header.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker sends a specially crafted HTTP request to a Node.js server that sits behind a reverse proxy or load balancer. The request contains a Content-Length header with a leading space character.

The front-end proxy interprets the Content-Length header correctly and forwards what it believes is the complete request. However, the Node.js back-end interprets the request boundaries differently due to the malformed header. This allows the attacker to embed a second, smuggled request that the back-end processes as a separate, legitimate request.

The attack can be leveraged to bypass security controls implemented at the proxy level, poison web caches with malicious content, hijack other users' requests by having the smuggled request processed as part of another user's session, or perform unauthorized actions on behalf of other users.

Detection Methods for CVE-2024-27982

Indicators of Compromise

• Unusual HTTP requests containing whitespace before header names in server logs
• Unexpected request boundaries or truncated requests in access logs
• Cache entries containing content that doesn't match expected responses
• Users reporting seeing other users' data or unexpected responses

Detection Strategies

• Implement deep packet inspection to detect HTTP requests with malformed headers containing leading whitespace
• Monitor web application firewall (WAF) logs for anomalous header patterns
• Configure reverse proxies to log and alert on requests with non-standard header formatting
• Deploy network intrusion detection signatures targeting HTTP smuggling patterns

Monitoring Recommendations

• Enable verbose HTTP request logging on both proxy and Node.js application servers to identify request boundary discrepancies
• Implement correlation analysis between front-end and back-end server logs to detect request smuggling attempts
• Set up alerts for unusual patterns in Content-Length or Transfer-Encoding header handling
• Monitor for cache poisoning indicators such as unexpected cache hit ratios or content mismatches

How to Mitigate CVE-2024-27982

Immediate Actions Required

• Update Node.js to the latest patched version immediately
• Configure front-end proxies to normalize or reject requests with malformed headers
• Implement strict HTTP request validation at the network perimeter
• Review and harden web application firewall rules to detect HTTP smuggling patterns

Patch Information

Security patches addressing this vulnerability have been released. Organizations should update their Node.js installations to the latest stable version. Security advisories have been published by multiple distributions including Debian LTS and Fedora. NetApp has also released a security advisory for affected products. The original vulnerability report is available on HackerOne.

Workarounds

• Configure reverse proxies to strictly validate HTTP headers and reject requests with leading whitespace in header names
• Implement a WAF rule to block requests containing space-prefixed headers
• Use HTTP/2 between front-end proxies and back-end servers where possible, as HTTP/2's binary framing prevents traditional smuggling attacks
• Ensure all components in the request chain (load balancers, proxies, application servers) are configured to handle ambiguous requests consistently

# Example nginx configuration to normalize headers
# Add to your server or location block
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;

# Ensure strict HTTP parsing
ignore_invalid_headers off;
underscores_in_headers off;