Cryptomator for Android Man-in-the-Middle Vulnerability in Hub Key Loading Mechanism

A vulnerability in Cryptomator for Android prior to version 1.12.3 allows an attacker to tamper with the vault configuration file, creating a man-in-the-middle vulnerability during the Hub key loading process. The client previously trusted endpoints from the vault configuration without verifying host authenticity, which could lead to token exfiltration by combining a legitimate authentication endpoint with a malicious API endpoint. This issue affects users unlocking Hub-backed vaults with versions prior to 1.12.3, in environments where an attacker can modify the vault.cryptomator file.

Impact

Exploitation of this vulnerability could result in a man-in-the-middle attack, allowing an attacker to intercept and potentially alter communications between the client and the Hub, specifically during the key loading process.

Remediation

Users can upgrade to Cryptomator version 1.12.3, which includes host verification during the unlock process. If an immediate upgrade is not possible, users can restrict network access to only trusted Hub hosts and protect the integrity of the vault configuration file by using strict file permissions and trusted sync or storage paths.