CVE-2002-1090 in libesmtp
Summary
by MITRE
Buffer overflow in read_smtp_response of protocol.c in libesmtp before 0.8.11 allows a remote SMTP server to (1) execute arbitrary code via a certain response or (2) cause a denial of service via long server responses.
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Analysis
by VulDB Data Team • 09/08/2025
The vulnerability described in CVE-2002-1090 represents a critical buffer overflow flaw within the libesmtp library version 0.8.10 and earlier. This issue specifically affects the read_smtp_response function located in the protocol.c file of the library. The buffer overflow occurs when processing SMTP server responses during email transmission, creating a security weakness that can be exploited by remote attackers. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which is a common and dangerous class of memory corruption vulnerabilities that can lead to arbitrary code execution or system instability. The flaw demonstrates how improper input validation in network protocol handling can create significant security risks for applications that rely on SMTP communication.
The technical implementation of this vulnerability stems from insufficient bounds checking when processing server responses from SMTP servers. When libesmtp receives a response from an SMTP server, the read_smtp_response function attempts to store this data in a fixed-size buffer without adequate validation of the response length. This allows a malicious SMTP server to craft responses that exceed the allocated buffer space, causing memory corruption that can be exploited to overwrite adjacent memory locations. The vulnerability can manifest in two distinct attack vectors as specified in the CVE description. The first vector enables remote code execution through carefully crafted responses that overwrite the program's instruction pointer, allowing attackers to inject and execute malicious code on the target system. The second vector provides a denial of service capability through excessively long responses that cause the application to crash or become unresponsive.
The operational impact of this vulnerability extends beyond simple exploitation as it affects the broader ecosystem of applications that depend on libesmtp for email functionality. Systems using vulnerable versions of this library become susceptible to remote attacks that could compromise email servers, mail clients, or any application that processes SMTP responses through this library. The vulnerability particularly affects email infrastructure components such as mail transfer agents, email clients, and automated email processing systems. Attackers can leverage this flaw to gain unauthorized access to systems, disrupt email services, or establish persistent access through code execution. The attack surface is broad as many email-related applications and services utilize libesmtp for SMTP protocol handling, making this vulnerability particularly dangerous for network administrators and security professionals managing email infrastructure. The vulnerability also aligns with ATT&CK technique T1203, which covers exploitation of remote services through buffer overflow attacks.
Mitigation strategies for CVE-2002-1090 primarily involve upgrading to libesmtp version 0.8.11 or later, which contains the necessary patches to address the buffer overflow vulnerability. Organizations should conduct thorough inventory assessments to identify all systems using vulnerable versions of the library and prioritize remediation efforts accordingly. Additional defensive measures include implementing network segmentation to limit exposure of systems that process SMTP traffic, deploying intrusion detection systems to monitor for suspicious SMTP responses, and configuring applications to use more secure SMTP libraries that have been audited for similar vulnerabilities. Security teams should also consider implementing input validation measures at network boundaries to filter out malformed SMTP responses that could trigger the buffer overflow condition. The vulnerability serves as a reminder of the importance of maintaining up-to-date security libraries and the critical need for proper input validation in network protocol implementations. Organizations should establish robust patch management processes to ensure timely deployment of security updates and conduct regular security assessments to identify and remediate similar vulnerabilities in their software dependencies.