CVE-2021-47971 Overview
CVE-2021-47971 is a denial of service vulnerability in My Notes Safe 5.3. The flaw allows attackers to crash the application by pasting excessively long character strings into note fields. A payload of 350,000 repeated characters pasted twice into a new note triggers an application crash. The vulnerability is classified under [CWE-789] Memory Allocation with Excessive Size Value. The issue affects the availability of the application but does not impact confidentiality or integrity. Public exploit code is available through Exploit-DB.
Critical Impact
Attackers can crash My Notes Safe 5.3 by submitting oversized character payloads to note fields, resulting in loss of availability.
Affected Products
- My Notes Safe 5.3
Discovery Timeline
- 2026-05-16 - CVE-2021-47971 published to NVD
- 2026-05-18 - Last updated in NVD database
Technical Details for CVE-2021-47971
Vulnerability Analysis
My Notes Safe 5.3 fails to validate or constrain the length of character input written to note fields. When a user pastes a string containing 350,000 repeated characters twice into a new note, the application allocates memory based on the attacker-controlled input size. The resulting allocation exceeds what the application can handle, causing it to crash. This pattern matches [CWE-789] Memory Allocation with Excessive Size Value, where the application allocates memory without sufficient bounds checking on the input size.
Root Cause
The root cause is missing input length validation in note field handling. The application does not enforce a maximum size on pasted content before allocating memory to store it. Memory allocation tied directly to untrusted input length creates a denial of service condition. No upper bound enforcement exists on the buffer used for note content.
Attack Vector
The attack requires user interaction with the My Notes Safe application. An attacker generates a payload of 350,000 repeated characters and pastes it twice into a new note. The application then attempts to process and store the oversized input and crashes. The Exploit-DB entry #49954 documents the proof of concept. See the Exploit-DB advisory and the VulnCheck Advisory for technical details. No remote network-based delivery mechanism is documented; the trigger requires local interaction with the application.
Detection Methods for CVE-2021-47971
Indicators of Compromise
- Unexpected crashes of the My Notes Safe process during normal user activity or after paste operations.
- Application crash dumps containing excessively long repeated character sequences in note buffers.
- Windows Application Event Log entries showing faulting module references tied to My Notes Safe 5.3.
Detection Strategies
- Monitor for repeated process termination events involving My Notes Safe across endpoints.
- Inspect crash dump artifacts for oversized string allocations associated with note content fields.
- Correlate application crash telemetry with clipboard paste activity preceding the crash.
Monitoring Recommendations
- Forward Windows Event Log Application channel data to a centralized log platform for crash analysis.
- Track endpoint process stability metrics for the My Notes Safe binary across the environment.
- Alert on repeated abnormal termination events for the same application within short time windows.
How to Mitigate CVE-2021-47971
Immediate Actions Required
- Identify all systems running My Notes Safe 5.3 and inventory exposure.
- Restrict use of the application to trusted users until a vendor-supplied fix is verified.
- Educate users about the crash condition and instruct them to avoid pasting untrusted bulk content.
Patch Information
No vendor patch advisory is referenced in the NVD record for CVE-2021-47971. Users should consult the vendor for an updated release that addresses input length validation on note fields. Review the VulnCheck Advisory for the latest remediation guidance.
Workarounds
- Avoid pasting large or untrusted content into My Notes Safe note fields.
- Limit installation of My Notes Safe 5.3 to systems where availability loss is acceptable.
- Replace the application with an alternative note-taking solution that enforces input length limits.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
