CVE-2019-9149 in Mailvelope
Summary
by MITRE
Mailvelope prior to 3.3.0 allows private key operations without user interaction via its client-API. By modifying an URL parameter in Mailvelope, an attacker is able to sign (and encrypt) arbitrary messages with Mailvelope, assuming the private key password is cached. A second vulnerability allows an attacker to decrypt an arbitrary message when the GnuPG backend is used in Mailvelope.
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Analysis
by VulDB Data Team • 07/03/2020
CVE-2019-9149 represents a critical security flaw in Mailvelope versions prior to 3.3.0 that fundamentally undermines the cryptographic security model of the extension. This vulnerability operates through a client-side API manipulation technique that bypasses the intended user interaction requirements for private key operations. The flaw specifically exploits the extension's handling of URL parameters, allowing attackers to craft malicious requests that trigger cryptographic operations without proper user consent or authentication. The vulnerability is particularly dangerous because it assumes that users have cached their private key passwords, which is a common security practice for convenience but creates a significant attack surface when combined with this API manipulation capability.
The technical implementation of this vulnerability stems from inadequate input validation and insufficient access control mechanisms within Mailvelope's client API. When an attacker modifies URL parameters, they can invoke signing and encryption functions that should normally require explicit user confirmation. This behavior violates the fundamental principle of cryptographic security where private key operations must be explicitly authorized by the user. The vulnerability operates at the application layer and specifically targets the extension's API endpoints that handle cryptographic operations, making it a direct violation of secure coding practices and standards such as those outlined in CWE-347. The attack vector is particularly insidious because it requires no local privilege escalation or complex exploitation techniques, relying instead on the manipulation of existing extension functionality.
The operational impact of CVE-2019-9149 extends far beyond simple message signing, as it provides attackers with the capability to perform unauthorized cryptographic operations on behalf of users. When the GnuPG backend is in use, a second vulnerability allows decryption of arbitrary messages, creating a complete compromise of the user's cryptographic security posture. This means that attackers can not only forge digital signatures but also decrypt sensitive communications that were intended to remain confidential. The vulnerability affects all users who have cached their private key passwords, which represents a significant portion of the user base that prioritizes convenience over maximum security. The implications are particularly severe for users who rely on Mailvelope for business communications, personal privacy, or security-critical applications where the integrity and confidentiality of messages are paramount.
Organizations and individual users should immediately update to Mailvelope version 3.3.0 or later to address this vulnerability, as the fix implements proper input validation and access control measures. The mitigation strategy should include clearing cached private key passwords and re-evaluating the security configuration of the extension. Security teams should monitor for any signs of exploitation and consider implementing additional network-based detection measures to identify potential abuse of the API manipulation techniques. This vulnerability aligns with ATT&CK technique T1552.001 for unsecured credentials and T1059.001 for command and scripting interpreter, as it leverages API manipulation to achieve unauthorized cryptographic operations. The incident underscores the importance of proper API security design and the need for explicit user consent mechanisms for all cryptographic operations, particularly in security-sensitive applications where user trust is paramount.