CVE-2018-25253: Termite 3.4 Buffer Overflow DoS Vulnerability

CVE-2018-25253 Overview

CVE-2018-25253 is a buffer overflow vulnerability affecting Termite 3.4, a serial terminal emulator application developed by CompuPhase. The vulnerability exists in the User interface language settings field and allows local attackers to cause a denial of service by supplying an excessively long string. By pasting a 2000-byte payload into the Settings User interface language field, attackers can crash the application, disrupting legitimate user operations.

Critical Impact

Local attackers can crash the Termite application by exploiting an out-of-bounds write vulnerability in the settings interface, resulting in denial of service.

Affected Products

• Termite 3.4

Discovery Timeline

• 2026-04-04 - CVE-2018-25253 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2018-25253

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a type of memory corruption flaw. The application fails to properly validate the length of user-supplied input in the User interface language settings field before copying it into a fixed-size buffer. When an attacker provides input that exceeds the buffer's allocated size, the excess data overwrites adjacent memory locations, corrupting application state and leading to a crash.

The attack requires local access to the system where Termite is installed. No authentication or special privileges are needed to exploit the vulnerability, and no user interaction beyond normal application use is required. The impact is limited to availability—the vulnerability does not appear to allow information disclosure or integrity violations in its current form.

Root Cause

The root cause is improper input validation in the User interface language settings processing code. The application allocates a fixed-size buffer for the language setting but does not enforce proper bounds checking when copying user input into this buffer. This allows data beyond the buffer boundary to overwrite adjacent memory, triggering undefined behavior and ultimately crashing the application.

Attack Vector

The attack is executed locally through the application's graphical user interface. An attacker with access to the Termite application navigates to the Settings dialog and locates the User interface language field. The attacker then pastes an excessively long string (approximately 2000 bytes) into this field. When the application attempts to process this oversized input, the buffer overflow occurs, causing the application to crash.

The vulnerability mechanism can be understood as follows: The settings dialog accepts arbitrary text input without length validation. When the input exceeds the expected buffer size, the application writes beyond allocated memory boundaries. This out-of-bounds write corrupts adjacent memory structures, leading to application instability and termination. Technical details and proof-of-concept information can be found in the Exploit-DB #45453 entry and the VulnCheck Denial of Service Advisory.

Detection Methods for CVE-2018-25253

Indicators of Compromise

• Unexpected crashes of the Termite application, particularly after settings modification attempts
• Application event logs showing memory access violations or buffer overflow exceptions originating from Termite
• Presence of unusually large strings in Termite configuration files or registry entries
• Windows Error Reporting (WER) crash dumps indicating termite.exe faults in settings-related code paths

Detection Strategies

• Monitor for process termination events associated with termite.exe that indicate abnormal exit codes
• Implement application whitelisting to detect unauthorized modifications to Termite installation files
• Use endpoint detection and response (EDR) solutions to identify buffer overflow exploitation patterns
• Review system event logs for repeated application crashes that may indicate active exploitation attempts

Monitoring Recommendations

• Configure Windows Event Log monitoring to alert on Application Error events (Event ID 1000) involving termite.exe
• Deploy SentinelOne agents with behavioral AI to detect memory corruption exploitation attempts
• Establish baseline application stability metrics to identify anomalous crash patterns
• Implement centralized logging for workstations running Termite to correlate potential attack activity

How to Mitigate CVE-2018-25253

Immediate Actions Required

• Restrict access to systems running Termite 3.4 to trusted users only
• Consider removing or disabling Termite on systems where it is not actively required
• Evaluate alternative serial terminal applications that have been audited for security vulnerabilities
• Apply principle of least privilege to limit user access to application configuration settings

Patch Information

No vendor patch information was available at the time of this writing. Users are advised to monitor the CompuPhase Termite Software page for potential updates or security fixes. Consider contacting the vendor directly for remediation guidance.

Workarounds

• Avoid pasting untrusted or excessively long content into Termite settings fields
• Use configuration management tools to lock down Termite settings and prevent unauthorized modifications
• Run Termite in a sandboxed environment to contain potential crash impacts
• Implement application-level controls to restrict settings modification capabilities

# Configuration example: Restrict write access to Termite configuration files
# Windows: Set read-only permissions on configuration directory
icacls "C:\Program Files\Termite" /deny "Users:(W)"

# Alternative: Run Termite with reduced privileges using Windows Sandbox
# or application virtualization technologies