DevOps & Linux5 min read•Updated 2026-09-04
Chmod 777 vs 755 Explained: Security Risks and Best Practices
Why you should never run 'chmod 777' on production web servers, and what to use instead.
MX
MultiToolX Technical Team
Security & DevOps
Key Takeaways
- chmod 777 grants Read, Write, and Execute permissions to everyone on the system (Owner, Group, and Others).
- World-writable files allow malicious web shells or unauthorized local users to overwrite scripts and execute malware.
- Recommended standard: chmod 755 for directories and chmod 644 for regular files.
1. The Extreme Security Dangers of Chmod 777
Developers often run 'chmod -R 777' when troubleshooting file upload permission errors. While this fixes the immediate write failure, it opens a catastrophic security vulnerability: any user or compromised process can modify, delete, or inject malicious code into your files.
2. The Correct Way to Fix Web Upload Errors
Instead of 777, assign directory ownership to the web server user (e.g., www-data or nginx) and set permissions to 755:
chown -R www-data:www-data /var/www/uploads
chmod 755 /var/www/uploads
Frequently Asked Questions
What is the difference between 755 and 644?
755 (rwxr-xr-x) includes execute permissions necessary for traversing directories. 644 (rw-r--r--) is for static files that should not be executed as programs.
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