CVE-2026-82853 in Nodemailer
Summary
by MITRE • 08/31/2026
Nodemailer versions before 8.0.5 contain an SMTP command injection vulnerability in the transport name option used in EHLO/HELO commands. The name parameter is concatenated directly into SMTP commands without sanitizing carriage return and line feed characters, allowing attackers to inject arbitrary SMTP commands for email spoofing and phishing attacks.
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Analysis
by VulDB Data Team • 08/31/2026
The vulnerability identified in Nodemailer versions prior to 8.0.5 represents a critical security flaw rooted in improper input validation within the transport configuration mechanism. Specifically, the issue affects how the library handles the name parameter when constructing EHLO or HELO commands during the SMTP handshake process. In standard email transmission workflows using Simple Mail Transfer Protocol, these initial greeting messages are essential for establishing communication between the client and the mail server. The flaw arises because Nodemailer concatenates user-supplied input directly into these protocol-level strings without performing adequate sanitization of control characters, particularly carriage return and line feed sequences. This lack of validation creates a classic command injection vector where malicious actors can manipulate the structure of SMTP commands by injecting newline characters to terminate the intended greeting message prematurely.
From a technical perspective, this vulnerability allows for arbitrary SMTP command injection because the underlying protocol is designed to accept multiple lines in certain contexts or interpret newlines as delimiters between distinct commands. By inserting carriage return and line feed sequences into the transport name option, an attacker can effectively break out of the EHLO or HELO context and append additional SMTP directives that are then executed by the mail server. This capability fundamentally undermines the integrity of the email transmission process. The injected commands could include operations such as setting different envelope recipients, modifying message headers, or even attempting to relay messages through unauthorized channels depending on the configuration and permissions of the target mail server.
The operational impact of this vulnerability is severe, primarily facilitating sophisticated phishing campaigns and email spoofing attacks. Attackers can exploit this flaw to forge sender addresses with greater precision by manipulating SMTP envelope data rather than just message headers, which are often more visible but easier for spam filters to detect. By injecting commands that alter the RCPT TO or MAIL FROM parameters indirectly through header manipulation enabled by the injection, attackers can make malicious emails appear as though they originate from trusted domains. This significantly increases the success rate of social engineering attacks because recipients and automated security systems may trust messages based on their apparent origin. Furthermore, this vulnerability could potentially be leveraged for open relay abuse if the mail server is misconfigured or lacks strict access controls, allowing attackers to use the compromised application as a proxy to send spam or malware distribution payloads at scale.
This issue aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command and more specifically relates to SMTP command injection which falls under broader categories of input validation failures. In terms of threat modeling, this vulnerability supports techniques associated with MITRE ATT&CK T1566 Phishing, particularly the sub-technique for spearphishing attachment or link delivery where sender reputation is manipulated. It also touches upon aspects of data manipulation and integrity violation as defined in various application security frameworks. The root cause is a failure to enforce strict input constraints on dynamic values that are embedded into protocol-specific strings, highlighting the importance of treating all external inputs as untrusted regardless of their perceived safety or source context within an application layer.
Mitigation strategies must prioritize immediate updates and defensive coding practices. Organizations utilizing Nodemailer should upgrade to version 8.0.5 or later where this specific input validation issue has been addressed by implementing strict sanitization routines that strip or escape carriage return and line feed characters from the transport name parameter before it is used in SMTP commands. For environments where immediate patching is not feasible, developers can implement a custom wrapper function that validates the transport configuration object to ensure no control characters are present in sensitive fields prior to passing them to Nodemailer. Additionally, implementing strict Content Security Policies and email authentication protocols such as SPF DKIM and DMARC can help mitigate some downstream effects by ensuring that even if spoofing is attempted, receiving servers will reject messages that fail these integrity checks. Regular security audits of third-party library configurations are essential to prevent similar injection vectors in other parts of the application stack.