CVE-2025-22871: Go net/http Request Smuggling Vulnerability

CVE-2025-22871 Overview

The net/http package improperly accepts a bare LF as a line terminator in chunked data chunk-size lines. This can permit request smuggling if a net/http server is used in conjunction with a server that incorrectly accepts a bare LF as part of a chunk-ext.

Critical Impact

This vulnerability permits HTTP request smuggling, allowing attackers to manipulate web traffic or execute unauthorized actions on a target server.

Affected Products

• net/http package in Go

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to Not Available
• 2025-04-08 - CVE CVE-2025-22871 published to NVD
• 2025-04-18 - Last updated in NVD database

Technical Details for CVE-2025-22871

Vulnerability Analysis

The vulnerability lies in the net/http package's handling of chunked transfer encoding. By accepting a lone LF as a valid line terminator, the package allows for request smuggling scenarios, where a malicious HTTP request might not be correctly parsed by intermediary systems, potentially bypassing security controls and leading to unauthorized access or data manipulation.

Root Cause

Failure to properly validate line terminators in HTTP chunk extensions allows improper interpretation of HTTP message boundaries.

Attack Vector

Network-based attackers can exploit this vulnerability by sending specially crafted HTTP requests with bare LF line terminators in chunked data.

GET / HTTP/1.1
Host: vulnerable-server.com
Transfer-Encoding: chunked

5\n
Hello\n0\n\n

Detection Methods for CVE-2025-22871

Indicators of Compromise

• Unexpected HTTP request behavior
• Anomalous traffic patterns related to chunked transfer encoding
• Log entries with improperly terminated HTTP headers

Detection Strategies

Utilize network traffic analysis to identify malformed HTTP requests with bare LF line terminators in chunk extensions. Implement IDS/IPS rules to flag unusual request formats.

Monitoring Recommendations

Constantly monitor web server logs and alerts for anomalous patterns indicative of request smuggling attempts. Employ network security devices to log and analyze detailed HTTP session information.

How to Mitigate CVE-2025-22871

Immediate Actions Required

• Update the net/http package to the latest patched version
• Implement web application firewall (WAF) rules to detect and block malformed requests
• Review application logic to ensure proper HTTP parsing

Patch Information

Ensure that Go installation is updated as per Go Advisory.

Workarounds

If updating is not immediately possible, consider deploying proxy servers to normalize HTTP requests and strip unexpected line terminators.

# Example Nginx configuration to normalize HTTP requests
server {
    listen 80;
    location / {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_pass http://backend;
    }
    # Normalize by removing bare LF
    proxy_http_version 1.1;
    proxy_buffering off;
}