CVE-2004-0833 in Linux
Summary
by MITRE
Sendmail before 8.12.3 on Debian GNU/Linux, when using sasl and sasl-bin, uses a Sendmail configuration script with a fixed username and password, which could allow remote attackers to use Sendmail as an open mail relay and send spam messages.
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Analysis
by VulDB Data Team • 06/05/2019
The vulnerability described in CVE-2004-0833 represents a critical security flaw in Sendmail versions prior to 8.12.3 running on Debian GNU/Linux systems that utilize SASL authentication components. This issue stems from a hardcoded authentication credential within the Sendmail configuration script, creating a persistent security weakness that significantly undermines the mail server's integrity and trustworthiness. The flaw specifically affects systems where both sasl and sasl-bin packages are installed, indicating a targeted vulnerability that exploits the integration between Sendmail's mail handling capabilities and SASL's authentication framework.
The technical implementation of this vulnerability involves a fixed username and password combination embedded within the Sendmail configuration script itself, rather than dynamically generated or properly secured credentials. This hardcoded approach creates a persistent backdoor that remote attackers can exploit to authenticate with the mail server without proper authorization. The configuration script's design fails to implement proper credential management practices, allowing any remote attacker who can access the system to leverage these fixed credentials for unauthorized mail relay operations. The vulnerability specifically manifests when Sendmail operates in a mode that requires SASL authentication, making the fixed credentials accessible to malicious actors attempting to exploit the service.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it enables attackers to utilize the compromised Sendmail server as an open mail relay for spam distribution. This capability transforms the vulnerable system from a legitimate mail server into a vector for mass email abuse, potentially affecting not only the compromised organization but also the broader internet ecosystem. The open relay functionality allows attackers to send spam messages through the compromised server without detection, leveraging the legitimate mail server's reputation to bypass spam filters and deliver malicious content to unsuspecting recipients. This abuse pattern directly violates the fundamental principles of mail server security and can result in the compromised server being blacklisted by major email providers.
Security professionals should recognize this vulnerability as a classic example of poor credential management and hardcoded secrets, which aligns with CWE-798, which addresses the use of hardcoded credentials in software. The attack pattern corresponds to techniques described in the MITRE ATT&CK framework under the T1190 category, which covers the exploitation of remote services for spam relay operations. Organizations should implement immediate mitigations including updating Sendmail to version 8.12.3 or later, removing the fixed credentials from the configuration, and implementing proper access controls for SASL authentication. Additionally, network administrators should deploy email filtering solutions and monitor for unusual mail relay activity to detect potential exploitation attempts.
The remediation process requires comprehensive system updates to ensure that the Sendmail configuration script properly handles authentication credentials without relying on hardcoded values. Security teams must also conduct thorough audits of all mail server configurations to identify similar vulnerabilities in other services or applications. The incident highlights the importance of following security best practices such as implementing proper credential rotation, utilizing secure configuration management, and conducting regular vulnerability assessments to prevent similar issues from occurring in the future. Organizations should also consider implementing additional security controls such as rate limiting, IP address restrictions, and monitoring for unauthorized authentication attempts to further protect their mail infrastructure from exploitation.