CVE-2026-32303 in cryptomator
Summary
by MITRE • 03/20/2026
Cryptomator encrypts data being stored on cloud infrastructure. Prior to version 1.19.1, an integrity check vulnerability allows an attacker to tamper with the vault configuration file leading to a man-in-the-middle vulnerability in Hub key loading mechanism. Before this fix, the client trusted endpoints from the vault config without host authenticity checks, which could allow token exfiltration by mixing a legitimate auth endpoint with a malicious API endpoint. Impacted are users unlocking Hub-backed vaults with affected client versions in environments where an attacker can alter the vault.cryptomator file. This issue has been patched in version 1.19.1.
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Analysis
by VulDB Data Team • 03/26/2026
The vulnerability described in CVE-2026-32303 represents a critical integrity check failure within the Cryptomator client application that undermines the security of cloud-based encrypted storage systems. This flaw specifically affects versions prior to 1.19.1 and demonstrates a fundamental weakness in how the application validates and authenticates endpoint configurations during the vault unlocking process. The vulnerability arises from the client's trust model where it accepts and utilizes endpoint information directly from the vault configuration file without implementing proper host authenticity verification mechanisms. This design flaw creates a pathway for attackers to manipulate the vault configuration file and subsequently compromise the entire encryption workflow.
The technical implementation of this vulnerability stems from the absence of cryptographic validation checks for the Hub key loading mechanism within Cryptomator's architecture. When users attempt to unlock Hub-backed vaults, the client reads configuration parameters from the vault.cryptomator file which contains endpoint addresses for authentication services. Prior to the patch in version 1.19.1, the application did not perform certificate pinning, hostname verification, or other forms of endpoint authenticity validation. This allows an attacker with the capability to modify the vault configuration file to substitute legitimate authentication endpoints with malicious counterparts that appear identical to the client but are controlled by the attacker. The vulnerability operates at the intersection of trust management and endpoint validation, creating a scenario where the client's trust in the configuration file translates directly into trust in potentially compromised endpoints.
The operational impact of this vulnerability extends beyond simple data integrity concerns to encompass complete credential compromise and potential unauthorized access to encrypted cloud storage. When an attacker successfully manipulates the vault configuration file, they can redirect the authentication flow to their own malicious endpoints while maintaining the appearance of legitimate services. This creates a man-in-the-middle attack scenario where authentication tokens and other sensitive information can be intercepted and exfiltrated without detection. The vulnerability specifically targets users who unlock Hub-backed vaults, which represents a significant portion of Cryptomator's user base that relies on cloud infrastructure for their encrypted storage solutions. The attack requires the presence of an attacker who can alter the vault.cryptomator file, typically in environments where network traffic can be intercepted or where file system access is compromised, making this vulnerability particularly dangerous in shared or untrusted network environments.
This vulnerability aligns with CWE-295, which addresses improper certificate validation, and demonstrates characteristics consistent with ATT&CK technique T1566 related to credential harvesting through social engineering and man-in-the-middle attacks. The flaw represents a failure in the application's secure communication protocols and highlights the importance of implementing proper endpoint validation mechanisms. Organizations using Cryptomator with affected versions should immediately implement mitigation strategies including verifying the integrity of vault configuration files through cryptographic checksums, implementing network monitoring to detect unusual authentication patterns, and ensuring that all client installations are updated to version 1.19.1 or later. The patch addresses the core issue by implementing host authenticity checks that validate endpoint certificates and ensure that the authentication endpoints match the expected cryptographic signatures, thereby preventing the injection of malicious endpoints into the configuration process. This vulnerability serves as a reminder of the critical importance of endpoint validation in distributed systems and the potential consequences of trusting configuration data without proper verification mechanisms.