CVE-2020-37126 in Free Desktop Clock
Summary
by MITRE • 02/05/2026
Free Desktop Clock 3.0 contains a stack overflow vulnerability in the Time Zones display name input that allows attackers to overwrite Structured Exception Handler (SEH) registers. Attackers can exploit the vulnerability by crafting a malicious Unicode input that triggers an access violation and potentially execute arbitrary code.
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Analysis
by VulDB Data Team • 02/06/2026
The vulnerability identified as CVE-2020-37126 resides within Free Desktop Clock version 3.0, specifically within the Time Zones display name input processing functionality. This represents a critical stack-based buffer overflow condition that fundamentally compromises the application's memory integrity and execution flow control. The flaw manifests when the application processes user-supplied Unicode input for time zone display names without adequate bounds checking or input validation mechanisms.
The technical exploitation of this vulnerability leverages the classic stack overflow vector through improper handling of structured exception handling registers. When attackers craft malicious Unicode input sequences, the application fails to validate the input length against the allocated buffer space, leading to memory corruption that overwrites the structured exception handler registers. This memory corruption directly impacts the application's ability to handle exceptions properly and creates a potential code execution pathway. The vulnerability specifically targets the SEH chain manipulation, which is a well-documented exploitation technique that allows attackers to redirect program execution flow toward malicious code.
From an operational impact perspective, this vulnerability presents significant risk to system security as it enables remote code execution capabilities without requiring authentication or privileged access. The attack surface extends beyond simple local exploitation since the vulnerable application could be targeted through various attack vectors including malicious websites, email attachments, or compromised software distributions. The Unicode input processing nature of the vulnerability suggests that attackers could utilize sophisticated encoding techniques to bypass standard input sanitization measures while maintaining the exploit effectiveness.
Security professionals should recognize this vulnerability as a variant of CWE-121, which specifically addresses stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflows. The exploitation pattern aligns with ATT&CK technique T1059.007, which involves the use of scripting languages to execute malicious code, and T1203, which focuses on exploitation of remote services. The SEH overwrite mechanism places this vulnerability within the ATT&CK framework's T1068 category, which addresses local privilege escalation through application vulnerabilities.
Mitigation strategies should prioritize immediate patching of the Free Desktop Clock application to version 3.1 or later, which contains the necessary input validation and buffer management fixes. Organizations should implement input validation controls at multiple layers including application-level sanitization, network-based intrusion prevention systems, and endpoint protection measures. Additionally, security teams should consider implementing runtime application self-protection mechanisms and monitoring for anomalous input patterns that might indicate exploitation attempts. Regular security assessments should include vulnerability scanning for similar buffer overflow conditions in other desktop applications and system components to prevent similar exploitation vectors.