CVE-2018-12019 in Enigmail
Summary
by MITRE
The signature verification routine in Enigmail before 2.0.7 interprets user ids as status/control messages and does not correctly keep track of the status of multiple signatures, which allows remote attackers to spoof arbitrary email signatures via public keys containing crafted primary user ids.
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Analysis
by VulDB Data Team • 03/27/2023
The vulnerability identified as CVE-2018-12019 represents a critical flaw in the Enigmail email encryption extension for Mozilla Thunderbird and other email clients. This security issue affects versions prior to 2.0.7 and stems from a fundamental weakness in how the signature verification routine processes user identifiers within public keys. The flaw specifically manifests when the system interprets user ids as status or control messages rather than as legitimate identity markers, creating a pathway for malicious actors to manipulate signature verification processes.
The technical implementation of this vulnerability resides in the improper state tracking mechanisms within Enigmail's cryptographic verification subsystem. When processing public keys containing crafted primary user ids, the system fails to maintain accurate status information for multiple signatures simultaneously. This mismanagement creates a condition where the verification routine cannot properly distinguish between legitimate signature operations and maliciously constructed control sequences. The flaw operates at the intersection of cryptographic protocol handling and user identity validation, making it particularly insidious as it exploits the trust model inherent in public key infrastructure systems.
The operational impact of this vulnerability extends beyond simple message integrity concerns to encompass complete signature spoofing capabilities. Remote attackers can leverage this weakness to generate convincing fake signatures that appear legitimate to recipients, effectively bypassing the security guarantees that digital signatures are designed to provide. This capability undermines the fundamental purpose of email encryption systems, allowing malicious actors to impersonate legitimate users, forge documents, or manipulate communications in ways that would normally be prevented by proper cryptographic verification. The vulnerability affects all email communications processed through Enigmail, making it a significant threat to email security in environments where the extension is deployed.
The flaw aligns with CWE-295 which addresses improper certificate validation and CWE-347 which covers improper verification of cryptographic signatures. From an adversary perspective, this vulnerability maps to ATT&CK technique T1566 which involves social engineering through email, and T1556 which encompasses credential access through manipulation of authentication systems. The attack vector requires minimal prerequisites as it exploits the inherent trust model of public key cryptography, making it particularly dangerous in environments where users rely on signature verification to confirm message authenticity. Organizations should prioritize immediate patching of Enigmail installations to version 2.0.7 or later, while implementing additional email monitoring procedures to detect potential signature spoofing attempts. Network administrators should also consider deploying email security solutions that can detect anomalous signature patterns and implement multi-factor authentication mechanisms to reduce the attack surface.