CVE-2019-25570 in Serial Terminal
Summary
by MITRE • 03/21/2026
RealTerm Serial Terminal 2.0.0.70 contains a denial of service vulnerability that allows local attackers to crash the application by supplying an excessively long string in the Port field. Attackers can paste a buffer of 1000 characters into the Port input field and click the open button to trigger a crash.
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Analysis
by VulDB Data Team • 03/27/2026
The vulnerability identified as CVE-2019-25570 represents a classic buffer overflow condition within RealTerm Serial Terminal version 2.0.0.70 that manifests as a denial of service scenario. This flaw resides in the application's input validation mechanisms for the Port field, where the software fails to properly handle excessively long string inputs. The vulnerability specifically affects the application's ability to process user-supplied data in the serial port configuration interface, creating a scenario where malformed input can cause the entire application to terminate unexpectedly.
From a technical perspective, this vulnerability demonstrates a fundamental flaw in memory management and input handling within the RealTerm application. When a user inputs a string exceeding the allocated buffer size in the Port field, typically around 1000 characters as specified in the vulnerability description, the application experiences a buffer overflow condition. This occurs because the software does not implement proper bounds checking or input sanitization before processing the user-provided data. The vulnerability falls under the CWE-121 category of stack-based buffer overflow, though it may also exhibit characteristics of heap-based buffer overflow depending on the specific implementation details.
The operational impact of this vulnerability extends beyond simple application instability, as it provides local attackers with a straightforward method to disrupt legitimate system operations. Since the vulnerability requires only local access to execute, it can be exploited by any user with access to the system where RealTerm is installed. The attack vector is particularly concerning because it can be executed through simple copy-paste operations, making it accessible to attackers with minimal technical expertise. When triggered, the application crash effectively prevents legitimate users from accessing serial communication functionality, which could be particularly problematic in environments where serial port monitoring and communication are critical for system operations.
This vulnerability aligns with several ATT&CK framework techniques, specifically T1499.004 which covers network denial of service attacks, and T1566.001 which involves spearphishing with a malicious attachment. The local privilege escalation aspect of this vulnerability also relates to T1068, where an attacker could leverage this flaw to gain additional system access. Organizations utilizing RealTerm for serial communication monitoring, embedded system development, or industrial control systems face significant risk from this vulnerability, as it can be exploited to disrupt critical communication channels without requiring external network access. The impact is particularly severe in industrial environments where serial port communication is fundamental to operational technology systems.
Mitigation strategies for this vulnerability should focus on both immediate patching and defensive measures. The most effective solution involves applying the vendor-provided update or patch that addresses the buffer overflow condition in the Port field input handling. Organizations should also implement input validation controls at the application level, ensuring that all user-supplied data is properly bounded before processing. Additionally, system administrators should consider implementing application whitelisting policies that restrict execution of vulnerable versions of RealTerm. Network segmentation and monitoring should be enhanced to detect potential exploitation attempts, while regular security assessments should be conducted to identify similar vulnerabilities in other serial communication tools and applications within the environment. The vulnerability demonstrates the importance of robust input validation and memory safety practices in serial communication software, particularly in environments where system availability is critical.