Non-Constant Time String Comparison

Affecting csrf-lite package, versions <=0.1.1

Overview

csrf-lite is a CSRF protection utility for framework-free node sites. Affected versions of the package are vulnerable to a timing attack.

While the CSRF protection itself works well and increases security, the library uses the built-in string comparison mechanism, ===, and not a time constant string comparison. As a result, the comparison will fail faster when the first characters in the token are incorrect. An attacker can use this difference to perform a timing attack, essentially allowing them to guess the CSRF token one character at a time.

You can read more about timing attacks in Node.js on the Snyk blog: https://snyk.io/blog/node-js-timing-attack-ccc-ctf/

Remediation

Update to version 0.1.2 or higher.

References

• https://github.com/isaacs/csrf-lite/pull/1
• https://snyk.io/blog/node-js-timing-attack-ccc-ctf/