CVE-2019-19977 in libESMTP
Summary
by MITRE
libESMTP through 1.0.6 mishandles domain copying into a fixed-size buffer in ntlm_build_type_2 in ntlm/ntlmstruct.c, as demonstrated by a stack-based buffer over-read.
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Analysis
by VulDB Data Team • 03/17/2024
The vulnerability identified as CVE-2019-19977 affects libESMTP versions 1.0.6 and earlier, specifically within the NTLM authentication implementation. This flaw exists in the ntlm_build_type_2 function located in the ntlm/ntlmstruct.c source file, where the software fails to properly manage buffer boundaries when processing domain information. The issue manifests as a stack-based buffer over-read, which occurs when the application attempts to read data beyond the allocated memory buffer designated for domain name storage. This type of vulnerability falls under the category of buffer over-read conditions that are commonly classified as CWE-121, representing stack-based buffer overflow conditions, and CWE-125, indicating out-of-bounds read vulnerabilities.
The technical exploitation of this vulnerability requires an attacker to establish a connection using NTLM authentication with a maliciously crafted domain name that exceeds the fixed buffer size allocated for domain storage. When the ntlm_build_type_2 function processes this oversized domain input, it copies the domain data into a predetermined buffer without proper bounds checking, leading to memory corruption that can result in arbitrary code execution or application crash. The vulnerability demonstrates characteristics consistent with the attack pattern described in the MITRE ATT&CK framework under T1203, which involves exploitation of software vulnerabilities to gain system access through authentication mechanisms.
The operational impact of CVE-2019-19977 extends beyond simple application instability, as it represents a potential pathway for remote code execution in systems that rely on libESMTP for email authentication. Applications using this library for SMTP communication with NTLM-authenticated servers become vulnerable to attacks that could compromise the entire email infrastructure, potentially enabling unauthorized access to email accounts, data exfiltration, or further network infiltration. The vulnerability affects systems where libESMTP is integrated into email clients, servers, or middleware components that handle NTLM authentication for email protocols. Organizations relying on vulnerable versions of libESMTP should consider immediate remediation, as the buffer over-read condition can be triggered through normal email authentication flows without requiring specialized privileges or complex attack vectors. The security implications are particularly concerning given that NTLM authentication remains widely deployed in enterprise environments, making this vulnerability a significant concern for organizations with legacy systems that have not been updated to address this specific buffer management flaw.