CVE-2014-5369 in Enigmail
Summary
by MITRE
Enigmail 1.7.x before 1.7.2 sends emails in plaintext when encryption is enabled and only BCC recipients are specified, which allows remote attackers to obtain sensitive information by sniffing the network.
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Analysis
by VulDB Data Team • 12/15/2024
The vulnerability identified as CVE-2014-5369 affects Enigmail versions 1.7.x prior to 1.7.2, representing a critical security flaw in email encryption functionality within the Mozilla Thunderbird environment. This issue specifically manifests when users configure their email client to encrypt messages while utilizing only blind carbon copy recipients, creating a scenario where the encryption mechanism fails to properly protect the email content. The flaw stems from improper handling of message encryption states when BCC recipients are present, resulting in plaintext transmission of sensitive information despite encryption being enabled. This vulnerability directly violates fundamental security principles by undermining the confidentiality assurances that users expect when implementing email encryption protocols.
The technical implementation flaw occurs within the Enigmail plugin's message processing logic where the encryption routine fails to properly evaluate recipient types when determining whether to encrypt email content. When only BCC recipients are specified, the encryption module incorrectly assumes that no recipients require encryption, leading to plaintext transmission of the entire message body. This represents a classic case of inadequate input validation and state management, classified under CWE-20 as "Improper Input Validation" and potentially CWE-310 as "Cryptographic Issues" due to the improper handling of encryption states. The flaw exists in the conditional logic that determines when to apply encryption, specifically failing to account for the presence of BCC recipients in the encryption decision process.
Operationally, this vulnerability creates significant risks for users who rely on email encryption for protecting sensitive communications. Remote attackers capable of performing network packet sniffing can intercept and read plaintext versions of emails that should have been encrypted, potentially exposing confidential information such as personal data, business secrets, or proprietary communications. The impact extends beyond individual privacy concerns to encompass potential corporate data breaches, regulatory compliance violations, and reputational damage for organizations that depend on encrypted email communications. The vulnerability is particularly concerning because it operates silently without alerting users to the failed encryption, making it difficult for recipients to detect that their communications were not properly secured. This aligns with ATT&CK technique T1074.001 for "Data Staged" and T1566.001 for "Phishing" as attackers could exploit this weakness to harvest sensitive information through passive network monitoring.
The recommended mitigations include immediate upgrading to Enigmail version 1.7.2 or later, which contains the necessary patches to properly handle encryption states when BCC recipients are present. System administrators should also implement additional monitoring to detect unusual email patterns that might indicate failed encryption attempts. Organizations should conduct security awareness training to educate users about the importance of verifying encryption status before sending sensitive information. The fix addresses the root cause by modifying the encryption decision logic to properly evaluate all recipient types regardless of whether they are specified in the To, CC, or BCC fields. Security teams should also consider implementing network-based detection mechanisms to identify potential plaintext email transmission patterns that could indicate exploitation of this vulnerability.