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Tampered vault configuration allows MITM attack on Hub API

High
SailReal published GHSA-876q-q3mm-fcvj Mar 20, 2026

Package

No package listed

Affected versions

< 1.12.3

Patched versions

1.12.3

Description

Impact

An integrity check vulnerability allows an attacker 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.

Important

Since Cryptomator Hub uses end-to-end encryption, vault data was never in danger.

We are not aware of any active exploitation of this vulnerability.

Patches

Version 1.12.3 adds the following mitigation mechanisms: Trust-on-first-contact (TOFU) host verification during unlock with explicit approval required by the user.

Workarounds

If upgrading is not immediately possible:

  1. Restrict outbound client network access so Cryptomator can only reach trusted Hub hosts.
  2. Protect vault configuration integrity (strict file permissions, trusted sync/storage paths).

References

N/A

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N

CVE ID

CVE-2026-32317

Weaknesses

Origin Validation Error

The product does not properly verify that the source of data or communication is valid. Learn more on MITRE.

Improper Validation of Integrity Check Value

The product does not validate or incorrectly validates the integrity check values or checksums of a message. This may prevent it from detecting if the data has been modified or corrupted in transmission. Learn more on MITRE.

User Interface (UI) Misrepresentation of Critical Information

The user interface (UI) does not properly represent critical information to the user, allowing the information - or its source - to be obscured or spoofed. This is often a component in phishing attacks. Learn more on MITRE.

Improper Restriction of Communication Channel to Intended Endpoints

The product establishes a communication channel to (or from) an endpoint for privileged or protected operations, but it does not properly ensure that it is communicating with the correct endpoint. Learn more on MITRE.