CVE-2021-47824: iDailyDiary 4.30 DoS Vulnerability

CVE-2021-47824 Overview

CVE-2021-47824 is a denial of service vulnerability affecting iDailyDiary version 4.30, a personal diary application developed by Splinterware. The vulnerability allows attackers to crash the application by exploiting improper input validation in the preferences tab name field. When a specially crafted buffer containing approximately 2,000,000 characters is pasted into the default diary tab name field, the application fails to properly validate the input length, resulting in an application crash.

Critical Impact

Attackers can cause the iDailyDiary application to crash, resulting in denial of service and potential data loss if unsaved diary entries exist at the time of the crash.

Affected Products

• iDailyDiary version 4.30
• Splinterware iDailyDiary (Windows desktop application)

Discovery Timeline

• 2026-01-16 - CVE CVE-2021-47824 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2021-47824

Vulnerability Analysis

This vulnerability stems from improper validation of user-supplied input in the preferences configuration interface. The application fails to enforce appropriate length restrictions on the diary tab name field, which is designed to accept relatively short string values for display purposes. When an excessively long string is provided, the application's memory handling cannot accommodate the oversized input, leading to resource exhaustion and subsequent application termination.

The vulnerability is classified under CWE-1284 (Improper Validation of Specified Quantity in Input), indicating that the application does not properly verify that user input falls within acceptable size boundaries before processing. This type of flaw is particularly concerning in desktop applications where user configuration data is trusted without adequate bounds checking.

Root Cause

The root cause of this vulnerability is the absence of input length validation in the preferences tab name input handler. The application's user interface accepts and attempts to process arbitrarily large strings without first checking whether the input size exceeds reasonable operational limits. This allows an attacker to trigger memory allocation failures or buffer overflows that destabilize the application state.

Attack Vector

The attack requires local access to the system where iDailyDiary is installed. An attacker must interact with the application's preferences dialog and paste an oversized buffer (approximately 2,000,000 characters) into the default diary tab name field. This triggers the denial of service condition, causing the application to crash.

The attack scenario involves:

1. Opening the iDailyDiary application on the target system
2. Navigating to the preferences or settings menu
3. Locating the default diary tab name configuration field
4. Pasting a specially crafted buffer of approximately 2,000,000 characters
5. The application crashes due to inability to handle the oversized input

For technical details regarding this vulnerability, refer to the Exploit-DB entry #49898 and the VulnCheck Advisory for iDailyDiary.

Detection Methods for CVE-2021-47824

Indicators of Compromise

• Unexpected crashes of the iDailyDiary.exe process without user-initiated shutdown
• Application crash logs indicating memory allocation failures or buffer overflow conditions
• Configuration files containing abnormally large strings in the tab name field
• Windows Event Log entries showing application faults for iDailyDiary

Detection Strategies

• Monitor for repeated iDailyDiary application crashes that may indicate exploitation attempts
• Implement file integrity monitoring on iDailyDiary configuration files to detect abnormally large entries
• Deploy endpoint detection solutions capable of identifying application crash patterns associated with denial of service attacks
• Review Windows Application Event Logs for fault events associated with the iDailyDiary executable

Monitoring Recommendations

• Enable crash dump collection for the iDailyDiary application to capture forensic data during failure events
• Configure endpoint monitoring to alert on suspicious iDailyDiary configuration file modifications
• Implement application whitelisting policies to ensure only legitimate users can modify application preferences

How to Mitigate CVE-2021-47824

Immediate Actions Required

• Restrict local access to systems where iDailyDiary is installed to trusted users only
• Consider removing iDailyDiary from production environments until a patch is available
• Back up diary data regularly to prevent data loss from unexpected application crashes
• Monitor for vendor updates from Splinterware regarding security patches

Patch Information

At the time of this analysis, no official patch has been confirmed from the vendor. Users should monitor the Splinterware Homepage for potential security updates or newer versions that address this vulnerability.

Workarounds

• Limit clipboard paste functionality within the application if possible through Group Policy or third-party tools
• Restrict application permissions to prevent unauthorized users from accessing preferences settings
• Implement endpoint protection solutions that can detect and block attempts to paste excessively large data into applications
• Consider migrating to alternative diary applications with better input validation controls until a patch is released