CVE-2012-3482 in Fetchmail
Summary
by MITRE
Fetchmail 5.0.8 through 6.3.21, when using NTLM authentication in debug mode, allows remote NTLM servers to (1) cause a denial of service (crash and delayed delivery of inbound mail) via a crafted NTLM response that triggers an out-of-bounds read in the base64 decoder, or (2) obtain sensitive information from memory via an NTLM Type 2 message with a crafted Target Name structure, which triggers an out-of-bounds read.
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Analysis
by VulDB Data Team • 12/21/2021
The vulnerability identified as CVE-2012-3482 affects fetchmail versions 5.0.8 through 6.3.21 and represents a critical security flaw in the email retrieval utility's handling of NTLM authentication. This issue specifically manifests when fetchmail operates in debug mode and encounters NTLM authentication challenges from remote servers. The vulnerability stems from inadequate input validation within the base64 decoder component of fetchmail's NTLM implementation, creating exploitable conditions that can be leveraged by malicious actors to compromise system integrity and availability.
The technical flaw manifests through two distinct attack vectors that exploit out-of-bounds memory read conditions. The first vector enables a denial of service attack where a crafted NTLM response triggers an out-of-bounds read in the base64 decoder, causing fetchmail to crash and resulting in delayed delivery of inbound mail messages. This creates a persistent disruption to email services while simultaneously allowing attackers to potentially identify system vulnerabilities through the crash behavior. The second vector involves information disclosure through crafted NTLM Type 2 messages containing manipulated Target Name structures, which also trigger out-of-bounds reads that can expose sensitive memory contents to remote attackers.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential data exposure and system compromise. When fetchmail crashes due to the first vector, it creates a denial of service condition that can persist until the service is manually restarted, affecting legitimate email delivery and potentially masking other security incidents. The information disclosure aspect poses additional risks as attackers can extract memory contents that may contain sensitive data such as authentication credentials, system configuration details, or other confidential information. The vulnerability affects systems that rely on fetchmail for email retrieval, particularly those configured to use NTLM authentication with external mail servers, creating widespread potential impact across enterprise email infrastructures.
This vulnerability aligns with CWE-125, which describes out-of-bounds read conditions in software implementations, and demonstrates the critical importance of proper input validation in authentication protocols. The issue also maps to ATT&CK technique T1190, which covers exploitation of vulnerabilities in remote services, and T1005, which involves data from local system storage. Organizations using fetchmail in debug mode with NTLM authentication should immediately implement mitigations including disabling debug mode, updating to patched versions, and implementing network segmentation to limit exposure to potentially malicious NTLM servers. The vulnerability highlights the necessity of thorough security testing for authentication protocols and proper memory management practices in email client implementations.