CVE-2026-32317: Cryptomator Auth Bypass Vulnerability

CVE-2026-32317 Overview

CVE-2026-32317 is an integrity check vulnerability in Cryptomator for Android that allows attackers to tamper with the vault configuration file, leading to a man-in-the-middle (MITM) vulnerability in the Hub key loading mechanism. Prior to version 1.12.3, the Cryptomator Android client trusted endpoints specified in the vault configuration file without performing host authenticity checks. This flaw could enable token exfiltration by mixing a legitimate authentication endpoint with a malicious API endpoint.

Critical Impact

Attackers who can modify the vault.cryptomator configuration file can redirect authentication tokens to malicious endpoints, potentially compromising sensitive encryption keys and user credentials for Hub-backed vaults.

Affected Products

• Cryptomator for Android versions prior to 1.12.3
• Google Android (as the platform)
• Hub-backed vault configurations

Discovery Timeline

• March 20, 2026 - CVE-2026-32317 published to NVD
• March 26, 2026 - Last updated in NVD database

Technical Details for CVE-2026-32317

Vulnerability Analysis

This vulnerability is classified under CWE-346 (Origin Validation Error), indicating that the application fails to properly verify the origin or authenticity of data before trusting it. The Cryptomator Android client processes configuration data from the vault.cryptomator file without validating that the specified API endpoints belong to legitimate Cryptomator Hub infrastructure.

When a user unlocks a Hub-backed vault, the client reads endpoint URLs from the vault configuration file. An attacker who can modify this configuration file—either through cloud storage compromise, network interception, or local access—can substitute the legitimate API endpoint with a malicious server while keeping the authentication endpoint legitimate. This creates a scenario where users authenticate against the real Cryptomator Hub service, but their tokens are then sent to an attacker-controlled endpoint.

The network-based attack vector requires low privileges but has high complexity, as the attacker must be able to alter the vault configuration file in the user's cloud storage or through another vector that allows file modification.

Root Cause

The root cause stems from insufficient validation of endpoint origins in the Hub key loading mechanism. The client implementation trusted URLs from the vault configuration file implicitly, without verifying that the authentication endpoint and API endpoint share the same origin or belong to Cryptomator's trusted infrastructure. This lack of host authenticity checking allowed an attacker to create a split-origin attack where authentication succeeds against a legitimate service, but sensitive tokens are transmitted to an untrusted destination.

Attack Vector

The attack requires the adversary to gain write access to the vault.cryptomator configuration file stored in the user's cloud storage. Once access is obtained, the attacker modifies the vault configuration to point the API endpoint to a malicious server while leaving the authentication endpoint unchanged. When the victim next unlocks their Hub-backed vault, the authentication flow proceeds normally against the legitimate Cryptomator Hub service. However, after successful authentication, the client sends the obtained tokens to the attacker's malicious API endpoint, enabling token exfiltration and potential subsequent access to the encrypted vault contents.

The vulnerability specifically impacts environments where an attacker can alter files in cloud storage, such as through compromised cloud credentials, shared access configurations, or network-level attacks on synchronization traffic.

Detection Methods for CVE-2026-32317

Indicators of Compromise

• Unexpected modifications to vault.cryptomator configuration files in cloud storage
• API endpoint URLs in vault configurations pointing to non-Cryptomator domains
• Authentication tokens or Hub-related network traffic directed to unknown external servers
• Discrepancies between authentication endpoint and API endpoint origins in vault configurations

Detection Strategies

• Monitor cloud storage audit logs for unauthorized modifications to vault.cryptomator files
• Implement file integrity monitoring for vault configuration files across synchronized devices
• Analyze network traffic for connections to suspicious endpoints during vault unlock operations
• Review Cryptomator application version across managed Android devices to identify vulnerable installations

Monitoring Recommendations

• Enable cloud storage provider audit logging to track all file modifications
• Deploy endpoint detection solutions capable of identifying suspicious network connections from the Cryptomator application
• Implement mobile device management (MDM) policies to track application versions and enforce updates
• Configure network security tools to alert on token transmission to non-whitelisted Cryptomator Hub endpoints

How to Mitigate CVE-2026-32317

Immediate Actions Required

• Update Cryptomator for Android to version 1.12.3 or later immediately
• Review recent vault configuration file changes in cloud storage for unauthorized modifications
• Rotate Hub credentials and vault passwords if tampering is suspected
• Verify the integrity of all vault.cryptomator files in active use

Patch Information

Cryptomator has addressed this vulnerability in version 1.12.3 for Android. The patch implements host authenticity checks to ensure that endpoint URLs in vault configurations are validated before trusting them. Users should update through the Google Play Store or download the patched version directly from the Cryptomator Android Release 1.12.3 page.

For detailed information about the vulnerability and the fix, refer to the GitHub Security Advisory GHSA-876q-q3mm-fcvj.

Workarounds

• Restrict write access to cloud storage folders containing vault configuration files until the patch can be applied
• Manually verify that all endpoint URLs in vault.cryptomator files point to legitimate Cryptomator domains before unlocking vaults
• Temporarily avoid using Hub-backed vaults on unpatched Cryptomator Android installations
• Consider using local-only vault configurations without Hub integration as an interim measure