FreshRSS Authentication Bypass Vulnerability in Nonce Handling

An authentication bypass vulnerability has been identified in FreshRSS, a self-hosted RSS aggregator, specifically in the edge branch versions 1.27.2-dev (57e1a37 - 00f2f04). The issue arises from a change in nonce length, which was increased from 40 to 64 characters. This modification led to the improper construction of the string used in the password verification process. The 'password_verify()' function was called with a concatenated string of the SHA-256 nonce and a portion of the bcrypt hash, rather than the raw user password. Bcrypt truncates input longer than 72 bytes, causing the verification to incorrectly succeed even when an incorrect password is provided. This vulnerability allows users to log in without the correct credentials.

Impact

Exploitation of this vulnerability allows for authentication bypass, enabling users to log in without providing the correct password.

Reproduction

To reproduce this vulnerability, attempt to log in to FreshRSS edge branch versions 1.27.2-dev (57e1a37 - 00f2f04) using any password. The login will be successful, regardless of the password entered.

Remediation

Users can update to FreshRSS version 1.27.2-dev (476e57b) to address this vulnerability.