# CVE-2021-47970: Macaron Notes 5.5 Denial of Service via Buffer Overflow

> Attackers can crash Macaron Notes by pasting excessively long strings into note fields, causing a denial of service.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 May 2026
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-4439-4hh6-5j2w

## What is CVE-2021-47970?

CVE-2021-47970 is a high-severity denial of service vulnerability in Macaron Notes, published on 16 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Macaron Notes 5.5 contains a denial of service vulnerability that allows attackers to crash the application by creating notes with excessively long character strings. Attackers can generate a payload containing 350000 repeated characters and paste it into a note field to trigger application crash and stop functionality.

Weakness: CWE-789 (Memory Allocation with Excessive Size Value)

## Which versions are affected by CVE-2021-47970?


## How do I fix CVE-2021-47970?

No fix has been published for CVE-2021-47970 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-47970 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-47970 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47970 and fix it if it is affected.

What it is: CVE-2021-47970 is a high-severity denial of service vulnerability in Macaron Notes, published on 16 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-47970 exists.

Affected product: Macaron Notes. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-47970/ (Markdown: https://insights.sbomify.com/CVE-2021-47970/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47970
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47970
- OSV: https://osv.dev/vulnerability/CVE-2021-47970

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47970/
Summaries are generated and may contain mistakes; the official description above is the record.