CVE-2021-47970 Overview
CVE-2021-47970 affects Macaron Notes 5.5, a note-taking application vulnerable to a denial of service condition triggered by excessive input length. Attackers can crash the application by pasting a string of approximately 350,000 repeated characters into a note field. The flaw is categorized under [CWE-789] Memory Allocation with Excessive Size Value, where the application fails to enforce input length limits before allocating memory. Exploitation requires no authentication and no user interaction beyond delivering the crafted input to the target application. Successful exploitation halts application functionality and can result in loss of unsaved user data.
Critical Impact
Remote attackers can crash Macaron Notes 5.5 by submitting a 350,000-character payload, causing complete loss of application availability.
Affected Products
- Macaron Notes 5.5
Discovery Timeline
- 2026-05-16 - CVE-2021-47970 published to NVD
- 2026-05-18 - Last updated in NVD database
Technical Details for CVE-2021-47970
Vulnerability Analysis
The vulnerability is a denial of service condition rooted in unbounded input handling within Macaron Notes 5.5. The application accepts arbitrarily long character strings in note input fields without enforcing length validation. When an attacker supplies a payload containing 350,000 repeated characters, the application attempts to process and store the input, triggering an unrecoverable failure. The application then crashes and stops functioning, denying access to all stored notes until restart.
This weakness aligns with [CWE-789] Memory Allocation with Excessive Size Value. The affected component allocates memory or processes string data without first validating that the input falls within safe operational bounds. The result is resource exhaustion or buffer-related fault conditions that terminate the process.
Root Cause
The root cause is missing input length validation on note content fields. The application does not impose a maximum character limit before allocating buffers or performing string operations. This omission allows a single malformed input to overwhelm the application's text-handling logic and trigger a fatal error.
Attack Vector
The attack vector is network-accessible delivery of a malicious payload to the Macaron Notes application. An attacker generates a string of 350,000 identical characters and pastes or imports it into a note field. No authentication, no privilege, and no user interaction beyond receiving the payload is required for the crash to occur. Public proof-of-concept code is available on Exploit-DB #49953 and described in the VulnCheck Advisory on Macaron Notes. No verified code examples are reproduced here; refer to the linked sources for the technical proof-of-concept.
Detection Methods for CVE-2021-47970
Indicators of Compromise
- Unexpected termination of the Macaron Notes process accompanied by application error dialogs or crash logs.
- Note files or clipboard content containing unusually large runs of repeated characters approaching or exceeding 350,000 bytes.
- Repeated application restart events on endpoints running Macaron Notes 5.5.
Detection Strategies
- Monitor process termination events for Macaron Notes and correlate with preceding clipboard or file-import activity.
- Inspect endpoint telemetry for note files containing low-entropy, high-length strings, which indicate padding-style denial of service payloads.
- Alert on user-reported application instability tied to recently opened or shared note content.
Monitoring Recommendations
- Track Macaron Notes application crash frequency across managed endpoints to identify clustered exploitation attempts.
- Capture Windows Application event log entries and crash dumps for forensic review when the application terminates unexpectedly.
- Review file system activity for newly written note files exceeding reasonable size thresholds for the user population.
How to Mitigate CVE-2021-47970
Immediate Actions Required
- Restrict use of Macaron Notes 5.5 on managed endpoints until a vendor-supplied fix is verified and deployed.
- Educate users not to paste content from untrusted sources into the application.
- Back up existing note data so that a crash does not result in permanent data loss.
Patch Information
No vendor patch information is published in the available references. Consult the VulnCheck Advisory on Macaron Notes for the latest remediation guidance and any updates regarding fixed versions.
Workarounds
- Replace Macaron Notes 5.5 with an alternative note-taking application that enforces input length limits.
- Use an editor or clipboard manager that truncates oversized strings before they reach the application.
- Isolate the application from untrusted input channels such as shared note files or imported documents.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
