CVE-2021-4017
📋 TL;DR
CVE-2021-4017 is a Cross-Site Request Forgery (CSRF) vulnerability in showdoc, a documentation tool. It allows attackers to trick authenticated users into performing unintended actions like modifying documentation or changing settings. All showdoc installations with authenticated users are affected.
💻 Affected Systems
- showdoc
📦 What is this software?
Showdoc by Showdoc
⚠️ Risk & Real-World Impact
Worst Case
Attackers could modify or delete all documentation, change administrative settings, or potentially compromise the entire showdoc instance if combined with other vulnerabilities.
Likely Case
Unauthorized modifications to documentation content, user permissions changes, or configuration alterations leading to data integrity issues.
If Mitigated
Minimal impact if proper CSRF protections are implemented and users follow security best practices.
🎯 Exploit Status
Exploitation requires the victim to be authenticated and visit a malicious page. CSRF attacks are well-understood and easy to implement.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Commit 654e871a3923e79076818a9a03533fe88222c871 or later
Vendor Advisory: https://github.com/star7th/showdoc/commit/654e871a3923e79076818a9a03533fe88222c871
Restart Required: No
Instructions:
1. Update showdoc to the latest version. 2. Apply commit 654e871a3923e79076818a9a03533fe88222c871. 3. Verify CSRF tokens are properly implemented in all forms.
🔧 Temporary Workarounds
Implement CSRF Protection Manually
allAdd CSRF tokens to all forms and validate them server-side.
Modify showdoc source code to include CSRF tokens in forms and validate them in corresponding endpoints.
Use SameSite Cookies
allConfigure session cookies with SameSite=Strict attribute to prevent CSRF attacks.
Set session cookie with 'SameSite=Strict' in your web server configuration or application code.
🧯 If You Can't Patch
- Implement a web application firewall (WAF) with CSRF protection rules
- Restrict showdoc access to trusted networks only and monitor for suspicious activity
🔍 How to Verify
Check if Vulnerable:
Check if your showdoc version is older than commit 654e871a3923e79076818a9a03533fe88222c871 by examining the source code or version metadata.Check Version:
Check the showdoc version in the web interface or examine the source code for the commit hash.Verify Fix Applied:
Verify that CSRF tokens are present in all forms and validated server-side. Test with a CSRF proof-of-concept to confirm protection.📡 Detection & Monitoring
Log Indicators:
- Multiple failed form submissions without CSRF tokens
- Unusual documentation modifications from unexpected IP addresses
Network Indicators:
- HTTP requests to showdoc endpoints without proper referer headers or CSRF tokens from external sources
SIEM Query:
source="showdoc_logs" AND (event="form_submission" AND csrf_token="missing" OR event="unauthorized_modification")