How the Mentioned CVE Works:
The vulnerability in Rack::Sendfile arises due to improper handling of the `X-Sendfile-Type` header. The middleware logs the header values without sanitizing them, allowing an attacker to inject malicious input containing newline characters. These newline characters can manipulate log entries, enabling log injection attacks. For example, an attacker could insert fake log entries or split legitimate entries across multiple lines, distorting the log file’s integrity. This can obscure attack traces, making it difficult for administrators to detect and respond to security incidents. The issue is particularly concerning in environments where log files are used for auditing or forensic analysis.
DailyCVE Form:
Platform: Rack
Version: <2.2.4
Vulnerability: Log Injection
Severity: Medium
Date: 2022-XX-XX
What Undercode Say:
Exploitation:
1. Crafting Malicious Headers:
An attacker can send an HTTP request with a manipulated `X-Sendfile-Type` header containing newline characters.
Example:
GET /file HTTP/1.1 Host: example.com X-Sendfile-Type: malicious\n[FAKE LOG ENTRY]
2. Log Manipulation:
The unsanitized header is logged, injecting fake entries or splitting legitimate ones.
Example Log Output:
[INFO] Request: GET /file [FAKE LOG ENTRY]
3. Obscuring Attacks:
Attackers can hide their activities by overwriting or distorting log entries.
Protection:
1. Update Rack:
Upgrade to Rack version 2.2.4 or later, where the vulnerability is patched.
Command:
gem update rack
2. Sanitize Inputs:
Implement input sanitization for headers before logging.
Example Code (Ruby):
sanitized_header = header_value.gsub(/[\r\n]/, '')
logger.info("Header: {sanitized_header}")
3. Disable Rack::Sendfile:
If not required, remove or disable the middleware.
Example:
config/application.rb config.middleware.delete Rack::Sendfile
4. Log Monitoring:
Use tools like Splunk or ELK Stack to detect anomalies in log files.
Example Query:
source="app.log" | search "\n" OR "\r"
References:
Additional Commands:
- Check Rack Version:
gem list rack
- Test for Vulnerability:
Use a tool like `curl` to send a test request:curl -H "X-Sendfile-Type: test\n[FAKE LOG]" http://example.com/file
- Analyze Logs:
Use `grep` to search for suspicious entries:
grep -E "\n|\r" /var/log/app.log
References:
Reported By: https://github.com/advisories/GHSA-8cgq-6mh2-7j6v
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